vmadc and vector mask-register logical instructions are commutable
and there is no merge operand for their pseudos.
We add isCommutable=1 for these pseudos to gain more optimization
opportunities.
This patch fixes part of https://github.com/llvm/llvm-project/issues/64422.
Does this make PseudoVMANDN and PseudoVMORN commutable? That would be incorrect