Add unnecessary break to switch statements that don't fall through

GCC 7 can't tell that it's unnecessary, so it complained.

 registerhandler.cpp:528:13: warning: this statement may fall through [-Wimplicit-fallthrough=]

Change-Id: Ia3e896da908f42939148fffd14c6a15f3ec05524
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/ios/iostoolhandler.cpp

@@ -624,6 +624,7 @@ void IosDeviceToolHandlerPrivate::subprocessHasData()
                 outputParser.addData(QByteArray(buf, rRead));
                 processXml();
             }
+            break;
         }
         case XmlEndProcessed:
             stop(0);