[llvm] [Mips] Fix fast isel for i16 bswap. (PR #103398)

[Craig Topper via llvm-commits]

topperc wrote:

Maybe this patch won't fix https://github.com/llvm/llvm-project/issues/103035. The godbolt link on that issue shows it goes through the `hasMips32r2` path not this path.

https://github.com/llvm/llvm-project/pull/103398