[llvm] [RISCV] Mark vmvNr.v as implicitly using vtype (PR #118414)

[Philip Reames via llvm-commits]

preames wrote:

> I had to update the llvm-mca tests, I'm not sure why adding a use affects the number of cycles. cc @mshockwave

LGTM as well, the mca change is at least reasonable if we're modeling a new runtime dependency which wasn't previously being modeled.  

https://github.com/llvm/llvm-project/pull/118414