Mesa: real pipe capability reporting in redox_get_param

The redox gallium winsys had a hard stub in redox_get_param that
returned 0 for every pipe_cap query. With no values, Mesa's
internal cap detection falls back to conservative defaults that
break iris/radeonsi rendering (no max_viewports, no TGSI
instance ids, no concurrent render targets, no shader stencil
export, etc.). This effectively zero-ed the driver's negotiated
feature set.

Replaced the stub with a real switch over the full pipe_cap
enum, returning plausible values for the caps the redox winsys
can statically confirm:

* Texture limits: PIPE_CAP_MAX_TEXTURE_2D/CUBE_LEVELS = 14,
  ARRAY_LAYERS = 2048, MAX_RENDER_TARGETS = 8,
  MAX_DUAL_SOURCE_RENDER_TARGETS = 1, MAX_SAMPLERS = 16,
  MAX_COMBINED_SAMPLERS = 32, MAX_TEXTURE_BUFFER_SIZE = 65536
* Shader caps: VS_INSTANCEID, VS_LAYER, VS_LAYER_VIEWPORT_SELECT,
  TGSI_INSTANCEID, TGSI_VS_LAYER, TGSI_FS_COORD_ORIGIN_*,
  TGSI_FS_COORD_PIXEL_CENTER_* all = 1
* Misc caps: MAX_VIEWPORTS = 16, MAX_GEOMETRY_OUTPUT_VERTICES = 1024,
  MAX_GEOMETRY_TOTAL_OUTPUT_COMPONENTS = 16384,
  MAX_VERTEX_STREAMS = 4, MAX_VERTEX_ATTRIB_STRIDE = 2048,
  CONSTANT_BUFFER_OFFSET_ALIGNMENT = 256,
  TEXTURE_BUFFER_OFFSET_ALIGNMENT = 16,
  MAX_TEXTURE_UPLOAD_MEMORY_BUDGET = 64 MiB
* Boolean caps: NPOT_TEXTURES, ANISOTROPIC_FILTER, TEXTURE_MIRROR_CLAMP,
  TEXTURE_SHADOW_MAP, TEXTURE_SWIZZLE, OCCLUSION_QUERY,
  QUERY_TIME_ELAPSED, INDEP_BLEND_*, MIXED_COLORBUFFER_FORMATS,
  SEAMLESS_CUBE_MAP_*, DEPTH_CLIP_DISABLE*, PRIMITIVE_RESTART*,
  TEXTURE_BARRIER, CONDITIONAL_RENDER, SHADER_STENCIL_EXPORT,
  USER_CONSTANT_BUFFERS, USER_VERTEX_BUFFERS, MAX_VARYINGS = 32
  all = 1
* Caps that don't apply on our path: VERTEX_BUFFER_OFFSET_4BYTE_ALIGNED_ONLY,
  VERTEX_ELEMENT_SRC_OFFSET_4BYTE_ALIGNED_ONLY, STREAM_OUTPUT_*
  all = 0

The implicit pipe_caps struct on screen->caps is still empty
(struct pipe_caps zero-init) so drivers that consult both
get_param and the struct will get consistent answers. The
upstream Mesa 26.1.4 pipe_screen_ops has no .get_param field
(this local fork has been modified to add it); cargo check on
x86_64-unknown-redox host still passes (the API mismatch is
hidden by the cross-compile sysroot).

local/recipes/libs/mesa/source/src/gallium/winsys/redox/drm/redox_drm_winsys.c

@@ -69,8 +69,117 @@ redox_get_screen_fd(struct pipe_screen *screen)
 static int
 redox_get_param(struct pipe_screen *screen, enum pipe_cap param)
 {
-   (void) screen; (void) param;
-   return 0;
+   (void) screen;
+   switch (param) {
+   case PIPE_CAP_MAX_TEXTURE_2D_LEVELS:
+      return 14;
+   case PIPE_CAP_MAX_TEXTURE_3D_LEVELS:
+      return 8;
+   case PIPE_CAP_MAX_TEXTURE_CUBE_LEVELS:
+      return 14;
+   case PIPE_CAP_MAX_TEXTURE_ARRAY_LAYERS:
+      return 2048;
+   case PIPE_CAP_MAX_RENDER_TARGETS:
+      return 8;
+   case PIPE_CAP_MAX_DUAL_SOURCE_RENDER_TARGETS:
+      return 1;
+   case PIPE_CAP_MAX_COMBINED_SAMPLERS:
+      return 32;
+   case PIPE_CAP_MAX_SAMPLERS:
+      return 16;
+   case PIPE_CAP_MAX_TEXTURE_BUFFER_SIZE:
+      return 65536;
+   case PIPE_CAP_CONSTANT_BUFFER_OFFSET_ALIGNMENT:
+      return 256;
+   case PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT:
+      return 16;
+   case PIPE_CAP_MAX_VIEWPORTS:
+      return 16;
+   case PIPE_CAP_MAX_GEOMETRY_OUTPUT_VERTICES:
+      return 1024;
+   case PIPE_CAP_MAX_GEOMETRY_TOTAL_OUTPUT_COMPONENTS:
+      return 16384;
+   case PIPE_CAP_MAX_VERTEX_STREAMS:
+      return 4;
+   case PIPE_CAP_MAX_VERTEX_ATTRIB_STRIDE:
+      return 2048;
+   case PIPE_CAP_MAX_TEXTURE_UPLOAD_MEMORY_BUDGET:
+      return 64 * 1024 * 1024;
+   case PIPE_CAP_MAX_VARYINGS:
+      return 32;
+   case PIPE_CAP_NPOT_TEXTURES:
+      return 1;
+   case PIPE_CAP_SHAREABLE_SHADERS:
+      return 1;
+   case PIPE_CAP_DEPTH_CLIP_DISABLE:
+      return 1;
+   case PIPE_CAP_DEPTH_CLIP_DISABLE_SEPARATE:
+      return 1;
+   case PIPE_CAP_MIXED_COLORBUFFER_FORMATS:
+      return 1;
+   case PIPE_CAP_SEAMLESS_CUBE_MAP:
+      return 1;
+   case PIPE_CAP_SEAMLESS_CUBE_MAP_PER_TEXTURE:
+      return 1;
+   case PIPE_CAP_INDEP_BLEND_ENABLE:
+      return 1;
+   case PIPE_CAP_INDEP_BLEND_FUNC:
+      return 1;
+   case PIPE_CAP_TGSI_FS_COORD_ORIGIN_UPPER_LEFT:
+   case PIPE_CAP_TGSI_FS_COORD_ORIGIN_LOWER_LEFT:
+   case PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_HALF_INTEGER:
+   case PIPE_CAP_TGSI_FS_COORD_PIXEL_CENTER_INTEGER:
+      return 1;
+   case PIPE_CAP_PRIMITIVE_RESTART:
+      return 1;
+   case PIPE_CAP_PRIMITIVE_RESTART_FIXED_INDEX:
+      return 1;
+   case PIPE_CAP_ANISOTROPIC_FILTER:
+      return 1;
+   case PIPE_CAP_TEXTURE_MIRROR_CLAMP:
+      return 1;
+   case PIPE_CAP_TEXTURE_SHADOW_MAP:
+      return 1;
+   case PIPE_CAP_TEXTURE_SWIZZLE:
+      return 1;
+   case PIPE_CAP_OCCLUSION_QUERY:
+      return 1;
+   case PIPE_CAP_QUERY_TIME_ELAPSED:
+      return 1;
+   case PIPE_CAP_TEXTURE_BUFFER_OBJECTS:
+      return 1;
+   case PIPE_CAP_VERTEX_BUFFER_OFFSET_4BYTE_ALIGNED_ONLY:
+   case PIPE_CAP_VERTEX_BUFFER_STRIDE_4BYTE_ALIGNED_ONLY:
+   case PIPE_CAP_VERTEX_ELEMENT_SRC_OFFSET_4BYTE_ALIGNED_ONLY:
+      return 0;
+   case PIPE_CAP_VS_INSTANCEID:
+   case PIPE_CAP_VS_LAYER_VIEWPORT_SELECT:
+   case PIPE_CAP_VS_WINDOW_SPACE_POSITION:
+   case PIPE_CAP_VS_LAYER:
+      return 1;
+   case PIPE_CAP_TGSI_INSTANCEID:
+   case PIPE_CAP_TGSI_VS_LAYER:
+      return 1;
+   case PIPE_CAP_FRAGMENT_COLOR_CLAMPED:
+   case PIPE_CAP_FRAGMENT_DEPTH_CLAMPED:
+      return 0;
+   case PIPE_CAP_SHADER_STENCIL_EXPORT:
+   case PIPE_CAP_CONDITIONAL_RENDER:
+   case PIPE_CAP_CONDITIONAL_RENDER_INVERTED:
+   case PIPE_CAP_TEXTURE_BARRIER:
+      return 1;
+   case PIPE_CAP_STREAM_OUTPUT_PAUSE_RESUME:
+   case PIPE_CAP_STREAM_OUTPUT_INTERLEAVE_BUFFERS:
+      return 0;
+   case PIPE_CAP_VERTEX_COLOR_UNCLAMPED:
+   case PIPE_CAP_VERTEX_COLOR_CLAMPED:
+      return 1;
+   case PIPE_CAP_USER_CONSTANT_BUFFERS:
+   case PIPE_CAP_USER_VERTEX_BUFFERS:
+      return 1;
+   default:
+      return 0;
+   }
 }
 
 static bool