[clang] [clang] Add `__bf16` Type Support Macros With Literal Suffix Support (PR #134214)

[Muhammad Bassiouni via cfe-commits]

bassiounix wrote:

Looks like that `BFloat16Format` for `amdgcn-amd-amdhsa` target is not properly initialized and the `hasBFloat16Type` method at [`clang/lib/Basic/Targets/AMDGPU.h`](https://github.com/llvm/llvm-project/blob/92923e517c2926eb94b7b6e403433ecf62953186/clang/lib/Basic/Targets/AMDGPU.h#L127) is using a dummy check to that is based on the triple value only. Also there's no overrides for a full type support.

The global value of `BFloat16Format` in `AMDGPUTI` is properly initialized.

I think `TargetInfo::adjust` at [`clang/lib/Basic/TargetInfo.cpp`](https://github.com/llvm/llvm-project/blob/92923e517c2926eb94b7b6e403433ecf62953186/clang/lib/Basic/TargetInfo.cpp#L409) may be the reason but I'm not sure

https://github.com/llvm/llvm-project/pull/134214