[clang] [Clang][AMDGPU] Add builtins for some buffer resource atomics (PR #149216)

[Anshil Gandhi via cfe-commits]

https://github.com/gandhi56 approved this pull request.

LGTM, assuming `gfx90a-insts` is the suitable attribute and there is another approval.

https://github.com/llvm/llvm-project/pull/149216