The base class of polymorphic classes is required to declare a destructor. Several of these are empty, and can thus be declared as defaulted. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Umang Jain <email@uajain.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>