[media] v4l: of: Correct v4l2_of_parse_endpoint() kernel-doc

The v4l2_of_parse_endpoint function kernel-doc says that the return value
is always 0. But that is not true since the function can fail and a error
negative code is returned on failure. So correct the kernel-doc to match.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/v4l2-of.c

@@ -146,7 +146,7 @@ static void v4l2_of_parse_parallel_bus(const struct device_node *node,
  * variable without a low fixed limit. Please use
  * v4l2_of_alloc_parse_endpoint() in new drivers instead.
  *
- * Return: 0.
+ * Return: 0 on success or a negative error code on failure.
  */
 int v4l2_of_parse_endpoint(const struct device_node *node,
 			   struct v4l2_of_endpoint *endpoint)