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

Looks like these got left behind when vleff isel was moved to
X86ISelDAGToDAG.cpp

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -7897,8 +7897,6 @@ const char *RISCVTargetLowering::getTargetNodeName(unsigned Opcode) const {
   NODE_NAME_CASE(SPLAT_VECTOR_I64)
   NODE_NAME_CASE(READ_VLENB)
   NODE_NAME_CASE(TRUNCATE_VECTOR_VL)
-  NODE_NAME_CASE(VLEFF)
-  NODE_NAME_CASE(VLEFF_MASK)
   NODE_NAME_CASE(VSLIDEUP_VL)
   NODE_NAME_CASE(VSLIDE1UP_VL)
   NODE_NAME_CASE(VSLIDEDOWN_VL)

llvm/lib/Target/RISCV/RISCVISelLowering.h

@@ -129,9 +129,6 @@ enum NodeType : unsigned {
   // Truncates a RVV integer vector by one power-of-two. Carries both an extra
   // mask and VL operand.
   TRUNCATE_VECTOR_VL,
-  // Unit-stride fault-only-first load
-  VLEFF,
-  VLEFF_MASK,
   // Matches the semantics of vslideup/vslidedown. The first operand is the
   // pass-thru operand, the second is the source vector, the third is the
   // XLenVT index (either constant or non-constant), the fourth is the mask