[llvm] [NVPTX] Enhance `mul.wide` and `mad.wide` peepholes (PR #150477)

[Alex MacLean via llvm-commits]

https://github.com/AlexMaclean commented:

Nice, I think this is a better direction than the previous iteration. One potential improvement would be to pull the other existing MUL_WIDE table-gen patterns into DAG-Combines so they can be folded to mad.wide as well. 

https://github.com/llvm/llvm-project/pull/150477