patches/syscall: add P1-acpiverb-enter-exit-s2idle.patch (Phase I)

Phase I: hardware-agnostic s2idle / Modern Standby support.

The patch adds two new AcpiVerb enum variants to upstream
redox-os/syscall 0.8.1:

* EnterS2Idle (= 3) — acpid requests the kernel enter s2idle.
* ExitS2Idle  (= 4) — acpid signals s2idle exit.

The kernel-side wire is in local/sources/kernel/src/scheme/acpi.rs
(see kernel master @ 7a38664 for the [patch.crates-io] update that
points Cargo at local/sources/syscall).

The patch is durable in the outer RedBear-OS repo so that:
* The upstream base is at local/sources/syscall/ (own git repo,
  no version change from 0.8.1).
* When upstream updates, the inner repo is rebased on
  upstream/master and this patch is re-applied to the new
  upstream HEAD.
* The same patch is also applied to local/sources/syscall/
  in the inner git history (commit cfa7f0c), so the local fork
  has the same content the build system uses.

Hardware-agnostic: works for any platform with Modern Standby
firmware (Dell, HP, Lenovo, LG Gram, etc.), not just LG Gram.

local/patches/syscall/P1-acpiverb-enter-exit-s2idle.patch

@@ -0,0 +1,34 @@
+diff --git a/src/flag.rs b/src/flag.rs
+index 455ec36..1dd5040 100644
+--- a/src/flag.rs
++++ b/src/flag.rs
+@@ -310,12 +310,29 @@ pub enum AcpiVerb {
+     ReadRxsdt = 1,
+     // no payload, just returns 0 or 1
+     CheckShutdown = 2,
++    /// Red Bear OS extension (Phase I): acpid requests the kernel
++    /// enter s2idle (Modern Standby / S0ix). The kernel sets
++    /// `S2IDLE_REQUESTED`; the idle path calls `mwait_loop()`. Read
++    /// payload (1 byte) returns the *previous* value of the flag.
++    /// Write payload is opaque (ignored by current kernel).
++    /// Mirrors Linux 7.1 `s2idle_enter()` in
++    /// `kernel/power/suspend.c:91`. Hardware-agnostic — works on
++    /// any platform with Modern Standby firmware (Dell, HP, Lenovo,
++    /// LG Gram, etc.), not just LG Gram.
++    EnterS2Idle = 3,
++    /// Red Bear OS extension (Phase I): acpid signals s2idle
++    /// exit. Kernel clears `S2IDLE_REQUESTED`. Read payload (1
++    /// byte) always returns 0. Mirrors Linux 7.1 `s2idle_wake()` in
++    /// `kernel/power/suspend.c:133`. Hardware-agnostic.
++    ExitS2Idle = 4,
+ }
+ impl AcpiVerb {
+     pub const fn try_from_raw(value: u64) -> Option<Self> {
+         Some(match value {
+             1 => Self::ReadRxsdt,
+             2 => Self::CheckShutdown,
++            3 => Self::EnterS2Idle,
++            4 => Self::ExitS2Idle,
+             _ => return None,
+         })
+     }