MIPSr5+MSA: Support FMAX/FMIN instructions

[wzssyqa]

The baseline of R6 has FMAX/FMIN instructions, while R5 doesn't have.
For R5, if we have MSA, we can use FMAX/FMIN from MSA.

[Cyanoxygen]

Please assign this to me as well.

[llvmbot]

@llvm/issue-subscribers-backend-mips

Author: YunQiang Su (wzssyqa)

The baseline of R6 has FMAX/FMIN instructions, while R5 doesn't have. For R5, if we have MSA, we can use FMAX/FMIN from MSA.