[media] of: move graph helpers from drivers/media/v4l2-core to drivers/of

This patch moves the parsing helpers used to parse connected graphs
in the device tree, like the video interface bindings documented in
Documentation/devicetree/bindings/media/video-interfaces.txt, from
drivers/media/v4l2-core/v4l2-of.c into drivers/of/base.c.

This allows to reuse the same parser code from outside the V4L2
framework, most importantly from display drivers.
The functions v4l2_of_get_next_endpoint, v4l2_of_get_remote_port,
and v4l2_of_get_remote_port_parent are moved. They are renamed to
of_graph_get_next_endpoint, of_graph_get_remote_port, and
of_graph_get_remote_port_parent, respectively.
Since there are not that many current users yet, switch all of
them to the new functions right away.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c
index e5ddf47..192c4aa 100644
--- a/drivers/media/i2c/mt9p031.c
+++ b/drivers/media/i2c/mt9p031.c
@@ -21,6 +21,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_gpio.h>
+#include <linux/of_graph.h>
 #include <linux/pm.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
@@ -29,7 +30,6 @@
 #include <media/mt9p031.h>
 #include <media/v4l2-ctrls.h>
 #include <media/v4l2-device.h>
-#include <media/v4l2-of.h>
 #include <media/v4l2-subdev.h>
 
 #include "aptina-pll.h"
@@ -943,7 +943,7 @@
 	if (!IS_ENABLED(CONFIG_OF) || !client->dev.of_node)
 		return client->dev.platform_data;
 
-	np = v4l2_of_get_next_endpoint(client->dev.of_node, NULL);
+	np = of_graph_get_next_endpoint(client->dev.of_node, NULL);
 	if (!np)
 		return NULL;