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

[Luke Lau via llvm-commits]

lukel97 wrote:

> > > Do we still compile this with a single vsetvli after this change https://godbolt.org/z/bvGd46zWa
> > 
> > 
> > Just checked, there's no change
> 
> This was what I should have sent, the integer version https://godbolt.org/z/f9bzqz6aq but it already has a vsetvli toggle. :(

I think this is because we don't do the sew/lmul ratio trick in the backwards local postpass. I ran #71657 on this and it's able to remove the toggle

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