[llvm] AMDGPU: Ensure both wavesize features are not set (PR #159234)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> This is common in graphics where you can have a single pipeline containing two shaders, like a vertex shader using wave32 and a pixel shader using wave64.

Also do you really *need* to do that? We could have a much simpler ABI if we just banned this and required those to inhabit separate modules, with different triple arches 



https://github.com/llvm/llvm-project/pull/159234