[clang] AMDGPU: Rename and add bf16 support for global_load_tr builtins (PR #86202)

[Changpeng Fang via cfe-commits]

changpeng wrote:

> Do you want to rename intrinsics as well? Because now intrinsic names do not match builtin names.

Do we have to match builtins with intrinsics? Renaming intrinsics here means we will have to duplicate the intrinsics. 

https://github.com/llvm/llvm-project/pull/86202