linux/mips: Correct values for SI_TIMER, SI_MESGQ, SI_ASYNCIO

See arch/mips/include/uapi/asm/siginfo.h

(backport <rust-lang#4292>)
(cherry picked from commit 1f8474e)

Author: snogge

src/unix/linux_like/mod.rs

@@ -1293,9 +1293,17 @@ pub const SI_LOAD_SHIFT: c_uint = 16;
 pub const SI_USER: c_int = 0;
 pub const SI_KERNEL: c_int = 0x80;
 pub const SI_QUEUE: c_int = -1;
-pub const SI_TIMER: c_int = -2;
-pub const SI_MESGQ: c_int = -3;
-pub const SI_ASYNCIO: c_int = -4;
+cfg_if! {
+    if #[cfg(not(any(target_arch = "mips", target_arch = "mips32r6")))] {
+        pub const SI_TIMER: c_int = -2;
+        pub const SI_MESGQ: c_int = -3;
+        pub const SI_ASYNCIO: c_int = -4;
+    } else {
+        pub const SI_TIMER: c_int = -3;
+        pub const SI_MESGQ: c_int = -4;
+        pub const SI_ASYNCIO: c_int = -2;
+    }
+}
 pub const SI_SIGIO: c_int = -5;
 pub const SI_TKILL: c_int = -6;
 pub const SI_ASYNCNL: c_int = -60;