[llvm] [TargetLowering] Prevent expandVectorFindLastActive from creating illegal vector types during vector op legalization. (PR #190914)

[Luke Lau via llvm-commits]

https://github.com/lukel97 approved this pull request.

I presume `TargetLowering::expandCttzElts` will run into the same issue, the lowerings are very similar. We should probably also fix it in another PR

https://github.com/llvm/llvm-project/pull/190914