[llvm] [AMDGPU] Add `nocreateundeforpoison` annotations (PR #166450)

[Krzysztof Drewniak via llvm-commits]

krzysz00 wrote:

Re general applicability ... I'm not so sure about that?

A load, for example, can return a poison, no?

https://github.com/llvm/llvm-project/pull/166450