[llvm] [NVPTX] Make i16x2 a native type and add supported vec instructions (PR #65432)

[via llvm-commits]

ThomasRaoux wrote:




> Thank you @Artem-B for the breakage analysis!
> 
> @ThomasRaoux I hope you don't mind, I'm going to revert this change to unbreak XLA.

Can we fix it forward? I'll prepare a patch.

https://github.com/llvm/llvm-project/pull/65432