[media] DT: export of_get_next_parent() for use by modules: fix modular V4L2

Currently modular V4L2 build with enabled OF is broken dur to the
of_get_next_parent() function being unavailable to modules. Export it to
fix the build.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/of/base.c

@@ -382,6 +382,7 @@ struct device_node *of_get_next_parent(struct device_node *node)
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
 	return parent;
 }
+EXPORT_SYMBOL(of_get_next_parent);
 
 /**
  *	of_get_next_child - Iterate a node childs