[DBGHELP][NDK][RTL] *RtlComputeCrc32(): Add 'const' to 2nd parameter (#6973)

and sync SAL2 annotations.

It didn't always warn in the past, our gutfeeling (we have *not* double-checked that thesis!) is that the warnings might have been triggered when 0.4.15-dev-958-g 237aa3a9c1 was committed

sdk/include/ndk/rtlfuncs.h

@@ -4436,7 +4436,7 @@ ULONG
 NTAPI
 RtlComputeCrc32(
     _In_ ULONG InitialCrc,
-    _In_ PUCHAR Buffer,
+    _In_ const UCHAR *Buffer,
     _In_ ULONG Length
 );