media: omap3isp: Fix missing unlock in isp_subdev_notifier_complete()

Add the missing unlock before return from function
isp_subdev_notifier_complete() in the init error
handling case.

Fixes: ba689d933361 ("media: omap3isp: Acquire graph mutex for graph traversal")
Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Sakari Ailus <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/platform/omap3isp/isp.c

···
 	mutex_lock(&isp->media_dev.graph_mutex);
 
 	ret = media_entity_enum_init(&isp->crashed, &isp->media_dev);
-	if (ret)
+	if (ret) {
+		mutex_unlock(&isp->media_dev.graph_mutex);
 		return ret;
+	}
 
 	list_for_each_entry(sd, &v4l2_dev->subdevs, list) {
 		if (sd->notifier != &isp->notifier)