[clang] [llvm] [X86][AMX] Support AMX-AVX512 (PR #114070)

[Alan Zhao via cfe-commits]

alanzhao1 wrote:

> FYI this is causing Chrome X86 MacOS builds to fail due to `error: unknown type name '__m512bh'`: https://crbug.com/378111077

As I mentioned in https://crbug.com/378111077#comment3, the issue is that we pull in avx512bf16intrin.h because `__SCE__` is not defined, but `__SSE2__` is also not defined, so we don't pull in the `typedef` for `__m512bh` (since they're guarded by macros that look for `__SSE2__`) and so on. We then pull in amxavx512intrin.h which was introduced in this PR which then fails to compile because we don't have the `typedef`s.

https://github.com/llvm/llvm-project/pull/114070