[llvm] [MIPS] Add FeatureMSA to i6400 and i6500 cores (PR #134985)

[Min-Yih Hsu via llvm-commits]

https://github.com/mshockwave commented:

just a non-blocking suggestion: it'll be nice if you test individual CPU's features like https://github.com/llvm/llvm-project/blob/main/clang/test/Driver/riscv-cpus.c

https://github.com/llvm/llvm-project/pull/134985