[llvm] [RISCV] Fold vmnot.m of an integer compare into the compare (PR #222553)

[Marton Moro via llvm-commits]

martonmoro wrote:

@lukel97 I've split the tests into separate commits like you asked and also switched them to take the vec as an argument and I also dropped the mask restriction. I think it is ready for another look whenever you have some time. Thank you! :) 

https://github.com/llvm/llvm-project/pull/222553