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

[Craig Topper via llvm-commits]

topperc wrote:

> Maybe this patch won't fix #103035. The godbolt link on that issue shows it goes through the `hasMips32r2` path not this path.

Looks like this will fix #103035.

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