6660319 [RISCV] Remove unused RISCV::VLEFF and VLEFF_MASK. NFC

Authored and Committed by Craig Topper 3 years ago
    [RISCV] Remove unused RISCV::VLEFF and VLEFF_MASK. NFC
    
    Looks like these got left behind when vleff isel was moved to
    X86ISelDAGToDAG.cpp