of: property: add missing kerneldoc for of_graph_get_endpoint_count()

of_graph_get_endpoint_count() doesn't have kerneldoc. Add it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://lore.kernel.org/r/87r0hrcvzk.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Rob Herring <robh@kernel.org>

drivers/of/property.c

@@ -812,6 +812,12 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
 }
 EXPORT_SYMBOL(of_graph_get_remote_port);
 
+/**
+ * of_graph_get_endpoint_count() - get the number of endpoints in a device node
+ * @np: parent device node containing ports and endpoints
+ *
+ * Return: count of endpoint of this device node
+ */
 int of_graph_get_endpoint_count(const struct device_node *np)
 {
 	struct device_node *endpoint;