[clang] [llvm] [NVPTX] Add builtins and intrinsics for conversions of new FP types (PR #134345)

[Srinivasa Ravi via llvm-commits]

Wolfram70 wrote:

@Artem-B and @AlexMaclean , could you please take another look to see if this change is good to go?

https://github.com/llvm/llvm-project/pull/134345