[llvm] [NVPTX] Support lowering of `(l)lround` (PR #183901)

[Mitch Briles via llvm-commits]

MitchBriles wrote:

> Did you see PR's #180058 (merged) and #180060 (still open but probably soon to be merged too)?

I did not. Correct me if I'm wrong, but it seems that will fix a more general issue for flang. This PR will also support `llc -march=nvtpt ...` for IR with calls to `lround` and `llround`.

https://github.com/llvm/llvm-project/pull/183901