of: fix reference counting in of_graph_get_endpoint_by_regs

BugLink: http://bugs.launchpad.net/bugs/1621113

commit 34276bb0 upstream.

The called of_graph_get_next_endpoint() already decrements the refcount
of the prev node, so it is wrong to do it again in the calling function.

Use the for_each_endpoint_of_node() helper to interate through the
endpoint OF nodes, which already does the right thing and simplifies
the code a bit.

Fixes: 8ccd0d0c
(of: add helper for getting endpoint node of specific identifiers)
Reported-by: David Jander <david@protonic.nl>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/of/base.c

@@ -2253,20 +2253,13 @@ struct device_node *of_graph_get_endpoint_by_regs(
 	const struct device_node *parent, int port_reg, int reg)
 {
 	struct of_endpoint endpoint;
-	struct device_node *node, *prev_node = NULL;
-
-	while (1) {
-		node = of_graph_get_next_endpoint(parent, prev_node);
-		of_node_put(prev_node);
-		if (!node)
-			break;
+	struct device_node *node = NULL;
 
+	for_each_endpoint_of_node(parent, node) {
 		of_graph_parse_endpoint(node, &endpoint);
 		if (((port_reg == -1) || (endpoint.port == port_reg)) &&
 			((reg == -1) || (endpoint.id == reg)))
 			return node;
-
-		prev_node = node;
 	}
 
 	return NULL;