[llvm] [AMDGPU] Add function attribute to force enable WQM (PR #82468)

[Carl Ritson via llvm-commits]

perlfu wrote:

> I'm a bit confused about the usecase. Instead of putting `amdgpu-requires-wqm` on a function that calls `llvm.amdgcn.softwqm`, couldn't you just call `llvm.amdgcn.wqm` instead?

For `llvm.amdgcn.wqm` this is largely true, but the interaction with WWM and `llvm.amdgcn.set.inactive` there is currently no other option, unless we split `set.inactive` into _soft_ and _strict_ variants.

https://github.com/llvm/llvm-project/pull/82468