[llvm] [NVPTX] Add TTI support for folding isspacep in InferAS (PR #114486)

[Gautam Chakrabarti via llvm-commits]

gchak wrote:

Could be taken up in a separate PR, but could we get these `nvvm.isspacep.*` intrinsics documented in the NVPTX usage guide?

https://github.com/llvm/llvm-project/pull/114486