Clean up QDebug operators for QDir

Change-Id: Ia0a9eb5058adde98f690288cfbbb62a82a75dc60
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>