[RISCV][Clang] Add vmv and vfmv series intrinsic functions.

Authored-by: Roger Ferrer Ibanez <rofirrim@gmail.com>
Co-Authored-by: Zakk Chen <zakk.chen@sifive.com>

Reviewed By: craig.topper, Jim

Differential Revision: https://reviews.llvm.org/D100266