[CodeGen] Fix bug in IncrementPointer

[david-arm]

Summary

In an earlier patch I meant to add the correct flags to the ADD
node when incrementing the pointer, but forgot to pass them to
SelectionDAG::getNode.

[kmclaughlin]

LGTM

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

if (MemVT.isScalableVector()) {
     SDNodeFlags Flags;
     SDValue BytesIncrement = DAG.getVScale(
         DL, Ptr.getValueType(),
         APInt(Ptr.getValueSizeInBits().getFixedSize(), IncrementSize));
     MPI = MachinePointerInfo(N->getPointerInfo().getAddrSpace());
     Flags.setNoUnsignedWrap(true);
     if (ScaledOffset)
       *ScaledOffset += IncrementSize;
-    Ptr = DAG.getNode(ISD::ADD, DL, Ptr.getValueType(), Ptr, BytesIncrement);
+    Ptr = DAG.getNode(ISD::ADD, DL, Ptr.getValueType(), Ptr, BytesIncrement,
+                      Flags);
   } else {
     MPI = N->getPointerInfo().getWithOffset(IncrementSize);
     // Increment the pointer to the other half.
     Ptr = DAG.getObjectPtrOffset(DL, Ptr, TypeSize::Fixed(IncrementSize));
   }
 }
 
 void DAGTypeLegalizer::SplitVecRes_BinOp(SDNode *N, SDValue &Lo,