[SelectionDAG] Fix typo in VPLoadStoreSDNode

[rogfer01]

Summary

There is no code that uses this base class yet, hence the typo went unnoticed when this class was added in D105871

[frasercrmck]

LGTM, thanks!

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

VPLoadStoreSDNode(ISD::NodeType NodeTy, unsigned Order, const DebugLoc &dl,
     assert(getAddressingMode() == AM && "Value truncated");
   }
 
   // VPLoadSDNode (Chain, Ptr, Offset, Mask, EVL)
   // VPStoreSDNode (Chain, Data, Ptr, Offset, Mask, EVL)
   // Mask is a vector of i1 elements;
   // the type of EVL is TLI.getVPExplicitVectorLengthTy().
   const SDValue &getOffset() const {
-    return getOperand(getOpcode() == ISD::MLOAD ? 2 : 3);
+    return getOperand(getOpcode() == ISD::VP_LOAD ? 2 : 3);
   }
   const SDValue &getBasePtr() const {
     return getOperand(getOpcode() == ISD::VP_LOAD ? 1 : 2);
   }
   const SDValue &getMask() const {
     return getOperand(getOpcode() == ISD::VP_LOAD ? 3 : 4);
   }
   const SDValue &getVectorLength() const {