[llvm] [AMDGPU][Attributor] Infer `inreg` attribute in `AMDGPUAttributor` (PR #101609)

[Shilei Tian via llvm-commits]

shiltian wrote:

@arsenm Good to know. In fact this can't be landed due to another [issue](https://github.com/llvm/llvm-project/issues/107447) as well.

https://github.com/llvm/llvm-project/pull/101609