greybus: svc: flush workqueue at connection exit

Make sure to flush the workqueue from hotplug and hotunplug events when
the svc connection is tore down.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/svc.c

@@ -709,6 +709,8 @@ static void gb_svc_connection_exit(struct gb_connection *connection)
 	if (device_is_registered(&svc->dev))
 		device_del(&svc->dev);
 
+	flush_workqueue(svc->wq);
+
 	connection->hd->svc = NULL;
 	connection->private = NULL;