[llvm] [RISCV] Clear vill for whole vector register moves in vsetvli insertion (PR #118283)

[Luke Lau via llvm-commits]

lukel97 wrote:

> Isn't the `Uses = []` overriding that?

Oh woops, I completely missed that. I'll open up another PR to fix that

https://github.com/llvm/llvm-project/pull/118283