[X86] Add a 'break;' to the end of the last case in a switch to avoid surprising the next person to add a case after this one. NFC

llvm/lib/Target/X86/X86ISelDAGToDAG.cpp

@@ -4410,6 +4410,8 @@ void X86DAGToDAGISel::Select(SDNode *Node) {
         ReplaceNode(Node, CNode);
         return;
       }
+
+      break;
     }
     }