[llvm] [RISCV] Update V0Defs after moving Src in peepholes (PR #107359)

[Philip Reames via llvm-commits]

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

LGTM

For anyone curious, I was initially concerned about the case where Def might change V0 itself, but realized that's prevented by the safe to move check.

https://github.com/llvm/llvm-project/pull/107359