[clang] [llvm] [NVPTX] Add support for PTX 8.6 and CUDA 12.6 (12.8) (PR #123398)

[Durgadoss R via llvm-commits]

https://github.com/durga4github approved this pull request.

The updates look good to me.

https://github.com/llvm/llvm-project/pull/123398