add missing break. inconsequential as the code shouldn't be reached, but

for correctness' sake, it should be there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106229 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -2393,6 +2393,7 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node,
   case ISD::ATOMIC_CMP_SWAP: {
     assert (0 && "atomic intrinsic not lowered!");
     Results.push_back(Node->getOperand(0));
+    break;
   }
   case ISD::DYNAMIC_STACKALLOC:
     ExpandDYNAMIC_STACKALLOC(Node, Results);