Fix warnings about unused private fields

avfaudioinputselectorcontrol.h:68:23: warning: private field 'm_service' is not used [-Wunused-private-field]

Change-Id: I5722a2d1bf592862af3a4d36554419a653662892
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>

src/plugins/avfoundation/camera/avfcamerametadatacontrol.h

@@ -55,7 +55,6 @@ public:
     QStringList availableMetaData() const;
 
 private:
-    AVFCameraService *m_service;
     QMap<QString, QVariant> m_tags;
 };