[llvm] [RISCV] Move vmv.v.v peephole from SelectionDAG to RISCVVectorPeephole (PR #100367)

[Philip Reames via llvm-commits]

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

LGTM to the current version of the code.  

https://github.com/llvm/llvm-project/pull/100367