[clang] [Clang][AMDGPU] Add a new builtin type for buffer rsrc (PR #94830)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> Just a note - and maybe this was already discussed above - is there good reason not to explicitly make this type a 128-bit scalar? The LLVM data layout already does this

I thought this was the 160 bit version? 

Can we have an opaque-but-sized type? The concern is exposing this as a raw pointer right away 

https://github.com/llvm/llvm-project/pull/94830