[llvm] [RISCV] and x (sub 0, y) -> andn x y (PR #129253)

[Gábor Spaits via llvm-commits]

spaits wrote:

Maybe it would make sense, to add this pattern here too:
https://github.com/llvm/llvm-project/pull/129253/files#diff-ba86baa771a0e1e054ae55bdf33db0b9e48193a3582bc2cd73825af8e4013633R490

https://github.com/llvm/llvm-project/pull/129253