QtGui: replace a Q_FOREACH loop with QList::op+=

Change-Id: I071705d6fdb4cec5bc357bda034c249b400147a9
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

src/gui/kernel/qguiapplication.cpp

@@ -1378,10 +1378,8 @@ void QGuiApplicationPrivate::init()
 
     // Load environment exported generic plugins
     QByteArray envPlugins = qgetenv("QT_QPA_GENERIC_PLUGINS");
-    if (!envPlugins.isEmpty()) {
-        foreach (const QByteArray &plugin, envPlugins.split(','))
-            pluginList << plugin;
-    }
+    if (!envPlugins.isEmpty())
+        pluginList += envPlugins.split(',');
 
     if (platform_integration == 0)
         createPlatformIntegration();