media: mc-entity: Add missing kerneldoc

The argument args is not documented, and the latest kernel version
complains about that.

This fixes the following warning:
Warning: include/media/media-entity.h:1394 function parameter 'args'
not described in 'media_entity_call'

Fixes: 48a7c4bac9 ("[media] docs-rst: improve the kAPI documentation for the mediactl")
Signed-off-by: Ricardo Ribalda <[email protected]>
Reviewed-by: Daniel Scally <[email protected]>
Reviewed-by: Laurent Pinchart <[email protected]>
Signed-off-by: Hans Verkuil <[email protected]>

include/media/media-entity.h

@@ -1387,6 +1387,7 @@ void media_remove_intf_links(struct media_interface *intf);
  * @entity: entity where the @operation will be called
  * @operation: type of the operation. Should be the name of a member of
  *	struct &media_entity_operations.
+ * @args: arguments for the operation.
  *
  * This helper function will check if @operation is not %NULL. On such case,
  * it will issue a call to @operation\(@entity, @args\).