Fixed QtMultimedia core namespace compilation.

Change-Id: Ie276a7766bd26f3e49b2bc9c1a28ec96f1e3e4b0
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.h

@@ -50,17 +50,15 @@
 
 #include <limits.h>
 
+class PlayerResourcePolicy;
+
 QT_BEGIN_NAMESPACE
 class QMediaPlaylist;
 class QMediaPlaylistNavigator;
 class QSocketNotifier;
-QT_END_NAMESPACE
-
-QT_USE_NAMESPACE
 
 class QGstreamerPlayerSession;
 class QGstreamerPlayerService;
-class PlayerResourcePolicy;
 
 class QGstreamerPlayerControl : public QMediaPlayerControl
 {
@@ -155,4 +153,6 @@ private:
     PlayerResourcePolicy *m_resources;
 };
 
+QT_END_NAMESPACE
+
 #endif