Break from loop once we've found a Layout

There's no point in going on.
I already fixed that in Applet a while ago but forgot that in Dialog and ConfigView.

Differential Revision: https://phabricator.kde.org/D4017

src/plasmaquick/configview.cpp

@@ -241,6 +241,7 @@ void ConfigViewPrivate::mainItemLoaded()
                 child->property("fillWidth").isValid() && child->property("fillHeight").isValid()
             ) {
             layout = child;
+            break;
         }
     }
     mainItemLayout = layout;

src/plasmaquick/dialog.cpp

@@ -780,6 +780,7 @@ void Dialog::setMainItem(QQuickItem *mainItem)
                         child->property("fillWidth").isValid() && child->property("fillHeight").isValid()
                    ) {
                     layout = child;
+                    break;
                 }
             }