Replace the stub no-op i915 bridge methods with real implementations:
* i915_gem_set_tiling: validates tiling_mode (0..=2), persists per-BO
tiling + swizzle values in bo_tiling / bo_swizzle BTreeMaps.
* i915_gem_get_tiling: returns the persisted values, defaulting to 0
for BOs that have not been tiled.
* i915_gem_set_domain: on write_domain == CPU, flushes the GGTT
(gtt.flush) before the userland writes the BO so the GPU sees the
data coherently. Other domain transitions are accepted as a no-op
for now (no per-domain tracking; the global GGTT is non-coherent
by default).
* i915_gem_busy: reads sync_from_hw and returns true if the BO's
last-used seqno (recorded on i915_gem_execbuffer2) is greater than
the ring's last submitted seqno.
* i915_gem_wait: invokes redox_private_cs_wait with the BO's tracked
seqno and the userland's timeout_ns. Converts the i64 timeout to
the wire-struct u64 with .max(0).
* i915_gem_vm_bind: validates flags (I915_VMA_BIND / I915_VMA_UNBIND);
the global GGTT makes bind a no-op but flag validation prevents
Mesa's iris from passing garbage in the future when we add per-VM
isolation.
* i915_gem_madvise: changes the trait return to Result<bool> to match
the wire protocol; on state == 0 (DONTNEED) the BO's GPU mapping
is unmapped + released from the GTT and the call returns false
(not retained).
* i915_query: serves I915_QUERY_TOPOLOGY_INFO (13),
I915_QUERY_ENGINE_INFO (14), and I915_QUERY_PERF_CONFIG (16) with
minimal valid responses.
* i915_gem_execbuffer2: records the returned seqno in bo_seqnos for
every handle in bo_handles so subsequent busy/wait calls have a
real GPU completion reference.
* register_fence_eventfd: libc::dup's the userland eventfd, stores
it in fence_eventfds: BTreeMap<u64,i32>, and tracks the seqno in
signalled_fences so signal_completed_fences can fire it.
* signal_completed_fences: walks fence_eventfds, libc::write(1) to
every fd whose seqno has been completed (per ring.last_seqno() after
sync_from_hw), then libc::close the fd. Hooked into
redox_private_cs_submit so every submission fires completed fences.
Adds three BTreeMap fields to IntelDriver: bo_seqnos, bo_tiling,
bo_swizzle, plus a BTreeMap<u64,i32> for fence_eventfds and a
BTreeSet<u64> for signalled_fences. All Mutex-protected.
vasilito
f2c4b6667b