[RISCV] Add intrinsics for vslide1up/down, vfslide1up/down instruction

This patch adds intrinsics for vslide1up, vslide1down, vfslide1up, vfslide1down.

Authored-by: Roger Ferrer Ibanez <rofirrim@gmail.com>
Co-Authored-by: ShihPo Hung <shihpo.hung@sifive.com>

Differential Revision: https://reviews.llvm.org/D93608