[GlobalISel] Fix the infinite loop issue in `commute_int_constant_to_rhs`

- When both operands are constant, the matcher runs into an infinite
  loop as the commutation should be applied only when LHS is a constant
  and RHS is not.

Reviewers: arsenm

Reviewed By: arsenm

Pull Request: https://github.com/llvm/llvm-project/pull/87426