[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.
> 
> Is that because of the mangling?
Right.  It was originally suggested to use  a single instrinsic "load_lr".  But eventually we use global_load_tr to indicate this is in global address space.  If we want to rename intrinsics here, it should be global_load_tr_b64 and global_load_tr_b128. 

We should rename intrinsic if users can use intrinsics directly. I think use-friendly is more important.

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