make MODULE_PLUGIN_TYPES assignment actually have an effect

it must be done before load()ing qt_plugin.prf.

Change-Id: I0ad31f8d9761b2d059d656c9e4f674c8a7cc88a6
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

src/multimedia/multimedia.pro

@@ -1,6 +1,12 @@
 TARGET = QtMultimedia
 QT = core-private network gui-private
 
+MODULE_PLUGIN_TYPES = \
+    mediaservice \
+    audio \
+    video/videonode \
+    playlistformats
+
 QMAKE_DOCS = $$PWD/doc/qtmultimedia.qdocconf
 
 load(qt_module)
@@ -67,11 +73,6 @@ ANDROID_FEATURES += \
     android.hardware.camera \
     android.hardware.camera.autofocus \
     android.hardware.microphone
-MODULE_PLUGIN_TYPES = \
-    mediaservice \
-    audio \
-    video/videonode \
-    playlistformats
 
 win32: LIBS_PRIVATE += -luuid