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

[Luke Lau via llvm-commits]

lukel97 wrote:

> 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.

Argh, now that you mention it this should actually be setting the definition to the one at Def->getNextNode().

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