Replace a few more "fall through" comments with LLVM_FALLTHROUGH

Follow up to r278902. I had missed "fall through", with a space.

llvm-svn: 278970
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index e6d80ca..16365c0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -1123,12 +1123,12 @@
         ReplaceNode(Node, ResultVals.data());
         return;
       }
+      LLVM_FALLTHROUGH;
     }
-      // FALL THROUGH
     case TargetLowering::Expand:
       if (ExpandNode(Node))
         return;
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     case TargetLowering::LibCall:
       ConvertNodeToLibcall(Node);
       return;