[llvm] [RISCV][VLOPT] Add support for vfmerge.vfm and vfmv.v.f (PR #146692)

[Philip Reames via llvm-commits]

https://github.com/preames commented:

Don't we also want the merge in getOperandLog2EEW?  Going purely by analogy to how we have the integer versions.

https://github.com/llvm/llvm-project/pull/146692