[llvm] [NVPTX] instcombine known pointer AS checks. (PR #112964)

[Artem Belevich via llvm-commits]

Artem-B wrote:

> > I think it should be done more similarly to how we do targetInstCombineIntrinsic
> 
> This, indeed, sounds like a better place to handle these intrinsics. Will do.

Done.

https://github.com/llvm/llvm-project/pull/112964