[llvm] [LLVM][NVPTX]: Add intrinsic for setmaxnreg (PR #77289)

[Guray Ozen via llvm-commits]

https://github.com/grypp approved this pull request.

Thank you for addressing the comments. It looks good to me, but let's wait for others to review it.

https://github.com/llvm/llvm-project/pull/77289