[llvm] [RISCV] Support f16 vmv.v.v and vmerge.vvm intrinsics with Zvfhmin. (PR #101457)

[Luke Lau via llvm-commits]

https://github.com/lukel97 approved this pull request.

Do the float vslide{up,down} patterns need handled too?

https://github.com/llvm/llvm-project/pull/101457