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

Phase I/J: the overlay patch backing the syscall
EnterS2Idle/ExitS2Idle extension. Verifies cleanly
against fresh upstream redox-os/syscall 0.8.1
(commit 79cb6d9).

Mirrors Linux 7.1:
* EnterS2Idle (= 3) — s2idle_enter() in
  kernel/power/suspend.c:91
* ExitS2Idle  (= 4) — s2idle_wake() in
  kernel/power/suspend.c:133

Hardware-agnostic: works for any platform with
Modern Standby firmware (Dell, HP, Lenovo, LG Gram,
etc.), not just LG Gram. Applied to local/sources/syscall
in the inner git history (commit d9f7a9e) and to base's
[patch.crates-io] redox_syscall = { path = "../syscall" }.

When upstream updates (periodic rebase via
'git fetch upstream && git rebase upstream/master' in
local/sources/syscall), this patch is re-applied to
the new upstream HEAD.

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,
+         })
+     }