[LegalizeTypes] Remove a few cases from SplitVectorOperand that should never happen. NFC

CTTZ, CTLZ, CTPOP, and FCANONICALIZE all have the same input and
output types so the operand should have already been legalized when the
result type was legalized.

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

@@ -2044,16 +2044,12 @@ bool DAGTypeLegalizer::SplitVectorOperand(SDNode *N, unsigned OpNo) {
     case ISD::FP_TO_UINT:
     case ISD::STRICT_FP_TO_SINT:
     case ISD::STRICT_FP_TO_UINT:
-    case ISD::CTTZ:
-    case ISD::CTLZ:
-    case ISD::CTPOP:
     case ISD::STRICT_FP_EXTEND:
     case ISD::FP_EXTEND:
     case ISD::SIGN_EXTEND:
     case ISD::ZERO_EXTEND:
     case ISD::ANY_EXTEND:
     case ISD::FTRUNC:
-    case ISD::FCANONICALIZE:
       Res = SplitVecOp_UnaryOp(N);
       break;