[llvm] [RISCV] Remove vmv.s.x and vmv.x.s lmul pseudo variants (PR #71501)

[Philip Reames via llvm-commits]

preames wrote:

I happened to talk with Craig offline yesterday and we discussed this patch a bit.  Craig had previous raised a question above which appears to have gotten lost in the review discussion.  He posted https://github.com/llvm/llvm-project/pull/75544 to land the test cases in tree, and this patch needs to be rebased over that one, and the fix for the issue flagged in my comment as I believe that should resolve some diffs in this one.

I'd also like to request that you split this patch into the integer subset and the floating point subset.  The original patch was integer only, and some of the confusion on the review is caused by the addition of the floating point without it being clearly called out.  

https://github.com/llvm/llvm-project/pull/71501