[llvm] [DAG] Fix Failure to reassociate SMAX/SMIN/UMAX/UMIN (PR #82175)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

Please can you fix the failing tests
```
Failed Tests (5):
  LLVM :: CodeGen/RISCV/rvv/fixed-vectors-strided-vpload.ll
  LLVM :: CodeGen/RISCV/rvv/fixed-vectors-vpload.ll
  LLVM :: CodeGen/X86/combine-smin.ll
  LLVM :: CodeGen/X86/combine-umax.ll
  LLVM :: CodeGen/X86/combine-umin.ll
```

https://github.com/llvm/llvm-project/pull/82175