[llvm] [SPIR-V] Support `nonuniformindex` intrsinsic in SPIRV CodeGen. (PR #162540)

[Dmitry Sidorov via llvm-commits]

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

@s-perron thank you for the explanation. Fine with me then.

https://github.com/llvm/llvm-project/pull/162540