[llvm] [AMDGPU] Change handling of unsupported non-compute shaders with HSA (PR #126798)

[Shilei Tian via llvm-commits]

shiltian wrote:

> This one is actually really super annoying and we should fix it properly. This also doesn't really belong in the IR verifier.

My reading is, `amdgpu_ps` functions should not exist for `amdhsa` OS. If it does, the input IR is broken *for* `amdhsa`. The IR itself might _not_ be really invalid, but just under certain circumstances. I'm not very sure that whether IR verifier is supposed to be target agnostic. For example, is the IR still valid (from the verifier's perspective) if I invoke `opt` or `llc` with a x86 IR (assume the IR has some x86 dedicated stuff) but the target triple is `amdgcn`?

https://github.com/llvm/llvm-project/pull/126798