[SelectionDAG] Use SDNode::op_iterator instead of SDNodeIterator. NFC

I think SDNodeIterator primarily exists because GraphTraits requires
an iterator that dereferences to SDNode*. op_iterator dereferences to
SDUse* which is implicitly convertible to SDValue.

This piece of code can use SDValue instead of SDNode* so we should
prefer to use the the more common op_iterator.

Author: topperc

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -2986,8 +2986,7 @@ bool TargetLowering::SimplifyDemandedBits(
       DemandedBits.isSubsetOf(Known.Zero | Known.One)) {
     // Avoid folding to a constant if any OpaqueConstant is involved.
     const SDNode *N = Op.getNode();
-    for (SDNode *Op :
-         llvm::make_range(SDNodeIterator::begin(N), SDNodeIterator::end(N))) {
+    for (SDValue Op : N->ops()) {
       if (auto *C = dyn_cast<ConstantSDNode>(Op))
         if (C->isOpaque())
           return false;