[media] dt3155v4l: fix incorrect mutex locking

A mutex_unlock was missing in the 'success' path of the open() call,
and also at one error path in the same function.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/media/dt3155v4l/dt3155v4l.c

@@ -398,7 +398,7 @@ dt3155_open(struct file *filp)
 		pd->field_count = 0;
 		ret = vb2_queue_init(pd->q);
 		if (ret < 0)
-			return ret;
+			goto err_request_irq;
 		INIT_LIST_HEAD(&pd->dmaq);
 		spin_lock_init(&pd->lock);
 		/* disable all irqs, clear all irq flags */
@@ -410,6 +410,7 @@ dt3155_open(struct file *filp)
 			goto err_request_irq;
 	}
 	pd->users++;
+	mutex_unlock(&pd->mux);
 	return 0; /* success */
 err_request_irq:
 	kfree(pd->q);