[RISCV][NFC] Fix unused variable warning.

[frasercrmck]

LGTM

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

SDValue RISCVTargetLowering::lowerVectorMaskExt(SDValue Op, SelectionDAG &DAG,
   }
 
   MVT ContainerVT = getContainerForFixedLengthVector(VecVT);
   MVT I1ContainerVT =
       MVT::getVectorVT(MVT::i1, ContainerVT.getVectorElementCount());
 
   SDValue CC = convertToScalableVector(I1ContainerVT, Src, DAG, Subtarget);
 
-  auto [Mask, VL] = getDefaultVLOps(VecVT, ContainerVT, DL, DAG, Subtarget);
+  SDValue VL = getDefaultVLOps(VecVT, ContainerVT, DL, DAG, Subtarget).second;
 
   MVT XLenVT = Subtarget.getXLenVT();
   SDValue SplatZero = DAG.getConstant(0, DL, XLenVT);
   SDValue SplatTrueVal = DAG.getConstant(ExtTrueVal, DL, XLenVT);
 
   SplatZero = DAG.getNode(RISCVISD::VMV_V_X_VL, DL, ContainerVT,
                           DAG.getUNDEF(ContainerVT), SplatZero, VL);
   SplatTrueVal = DAG.getNode(RISCVISD::VMV_V_X_VL, DL, ContainerVT,