[llvm] [AMDGPU] Add new llvm.amdgcn.wave.shuffle intrinsic (PR #167372)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

Throw in some GFX6 & GFX9 tests, but apart from that and the inline comment it LGTM.

https://github.com/llvm/llvm-project/pull/167372