[llvm] [MIPS] Fix missing ANDI optimization (PR #97689)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson approved this pull request.

I don't work on MIPS anymore but this looks correct to me.

One nit: I think it would be good to pre-commit the test with the existing codegen first and then have this patch show the codegen improvement.

https://github.com/llvm/llvm-project/pull/97689