[media] use a function for DVB media controller register

This is really a simple function, but using it avoids to have
if's inside the drivers.

Also, the kABI becomes a little more clearer.

This shouldn't generate any overhead, and the type check
will happen when compiling with MC DVB enabled.

So, let's do it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/common/siano/smsdvb-main.c

@@ -1104,9 +1104,7 @@ static int smsdvb_hotplug(struct smscore_device_t *coredev,
 		pr_err("dvb_register_adapter() failed %d\n", rc);
 		goto adapter_error;
 	}
-#ifdef CONFIG_MEDIA_CONTROLLER_DVB
-	client->adapter.mdev = coredev->media_dev;
-#endif
+	dvb_register_media_controller(&client->adapter, coredev->media_dev);
 
 	/* init dvb demux */
 	client->demux.dmx.capabilities = DMX_TS_FILTERING;