of_graph: add of_graph_get_endpoint_count()

OF graph want to count its endpoint number, same as
of_get_child_count(). This patch adds of_graph_get_endpoint_count()

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index 9db632d..3e058f0 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -43,6 +43,7 @@
 #ifdef CONFIG_OF
 int of_graph_parse_endpoint(const struct device_node *node,
 				struct of_endpoint *endpoint);
+int of_graph_get_endpoint_count(const struct device_node *np);
 struct device_node *of_graph_get_port_by_id(struct device_node *node, u32 id);
 struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
 					struct device_node *previous);
@@ -64,6 +65,11 @@
 	return -ENOSYS;
 }
 
+static inline int of_graph_get_endpoint_count(const struct device_node *np)
+{
+	return 0;
+}
+
 static inline struct device_node *of_graph_get_port_by_id(
 					struct device_node *node, u32 id)
 {