[llvm] [MIPS]: Rework atomic max/min expand for subword (PR #89575)

[YunQiang Su via llvm-commits]

wzssyqa wrote:

How to test:
```
./bin/clang --target=mips-linux-gnu -O2 -mips32r2 max.c ../llvm/test/CodeGen/Mips/atomic-min-max.ll -g -static && ./a.out
```
[max.c.gz](https://github.com/llvm/llvm-project/files/15058762/max.c.gz)


https://github.com/llvm/llvm-project/pull/89575