[clang] [Clang][AMDGPU] Add builtins for instrinsic `llvm.amdgcn.raw.buffer.store` (PR #94576)

[Krzysztof Drewniak via cfe-commits]

krzysz00 wrote:

The thing is, in all the usecases I've seen, `soffsset == 0`, and so you can legalize on `voffset` (voffset is also what the constant offsets on an instruction get added to)

https://github.com/llvm/llvm-project/pull/94576