[llvm] [NVPTX] Add patterns for fma.relu.{f16|bf16} (PR #114977)

[Artem Belevich via llvm-commits]

https://github.com/Artem-B commented:

We will eventually want to figure out a way to effectively use f16x2 and bf16x2 variants of `fma.rn.relu`. 

https://github.com/llvm/llvm-project/pull/114977