[llvm] AMDGPU/gfx12: avoid crashing on legacy waitcnt intrinsics (PR #92306)

[Nicolai Hähnle via llvm-commits]

nhaehnle wrote:

> @nhaehnle do you think it is worth backporting this to the 18.x release branch? (If so I'm happy to do it.)

I doubt it.

https://github.com/llvm/llvm-project/pull/92306