device property: Add a macro for interating over graph endpoints

Add a convenience macro for iterating over graph endpoints. Iterating over
graph endpoints using fwnode_graph_get_next_endpoint() is a recurring
pattern, and this macro allows calling that function in a slightly more
convenient way. For instance,

	for (child = NULL;
	     (child = fwnode_graph_get_next_endpoint(fwnode, child)); )

becomes

	fwnode_graph_for_each_endpoint(fwnode, child)
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/property.h

@@ -293,6 +293,10 @@ struct fwnode_handle *
 fwnode_graph_get_remote_node(const struct fwnode_handle *fwnode, u32 port,
 			     u32 endpoint);
 
+#define fwnode_graph_for_each_endpoint(fwnode, child)			\
+	for (child = NULL;						\
+	     (child = fwnode_graph_get_next_endpoint(fwnode, child)); )
+
 int fwnode_graph_parse_endpoint(const struct fwnode_handle *fwnode,
 				struct fwnode_endpoint *endpoint);