[CodeGen] Fix incorrect pattern FMLA_* pseudo instructions

* Remove the incorrect patterns from AArch64fmla_p/AArch64fmls_p
* Add correct patterns to AArch64fmla_m1/AArch64fmls_m1
* Refactor fma_patfrags for the sake of PatFrags

Fixes https://github.com/llvm/llvm-project/issues/64419

Differential Revision: https://reviews.llvm.org/D157095