[llvm] [RISCV] Simplify PatSetCC_m and PatFprFprDynFrm_m (PR #68562)

[Wang Pengcheng via llvm-commits]

wangpc-pp wrote:

I think we don't need `PatSetCC_m` and `PatFprFprDynFrm_m` any more since there is just one def. So the usages of them can be replaced by `PatSetCC` and `PatFprFprDynFrm`. Or, to simplify some code, they can be subclasses (with suitable names without postfix `_m`) of `PatSetCC` and `PatFprFprDynFrm`.

https://github.com/llvm/llvm-project/pull/68562