Fix warnings introduced by r165826.

llvm-svn: 165829
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index a00f60f..4161078 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1739,6 +1739,8 @@
     case attr::AcquiredBefore:
     case attr::AcquiredAfter:
       return false;
+    default:
+      ;
   }
 
   const OwnershipAttr *OA = dyn_cast<OwnershipAttr>(A);