An empty props array is unnecessary, we can just not call
device_class_set_props().

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-id: 20201211220529.2290218-2-ehabkost@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>