[MSVC, ARM64] Fix signature for __prefetch (#93235)

#67174 added the `__prefetch` intrinsic, however it used the wrong
signature: the argument should be `const void*`, not `void*`.

Docs:
https://learn.microsoft.com/en-us/cpp/intrinsics/arm64-intrinsics?view=msvc-170#:~:text=__prefetch

Unfortunately, this can't be backported (there are no more 18.x
releases, and this change is a breaking change), so I'll see if I can
get a workaround added on MSVC's side for Clang 18.