[llvm] [NVPTX] Preserve v16i8 vector loads when legalizing (PR #67322)

[Pierre-Andre Saulais via llvm-commits]

pasaulais wrote:

I didn't know about v2 variants, thanks. This is something I'd rather revisit in a future PR as this is quite an old patch now and I still need to create a PR for the second part of the original changes once this is merged.

https://github.com/llvm/llvm-project/pull/67322