Revert "[VP][RISCV] Add vp.fshl/fshr and RISC-V support."

This reverts commit 70de0e01.

I'm seeing:

Failed Tests (2):
  LLVM :: CodeGen/RISCV/rvv/fixed-vectors-fshr-fshl-vp.ll
  LLVM :: CodeGen/RISCV/rvv/fshr-fshl-vp.ll

Also reported at:

https://lab.llvm.org/buildbot/#/builders/123/builds/14531