[clang] [Clang][HIP] Deprecate the AMDGCN_WAVEFRONT_SIZE macros (PR #112849)

[Alex Voicu via cfe-commits]

AlexVlx wrote:

> Just a heads up, this change is gonna break some OpenMP tests, specifically those prefix with `ompx`.

Just to clarify, adding the deprecation warning will break them, or the eventual, as-of-yet not-scheduled, removal, will?

https://github.com/llvm/llvm-project/pull/112849