of: add 'const' for of_parse_phandle parameter *np

The existing function does not change the passed device_node pointer. It is
only handed to of_get_property which itself takes a const struct device_node.

of_parse_phandle() can therefore take a const pointer as well.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
[grant.likely: drop extraneous whitespace change]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/include/linux/of.h b/include/linux/of.h
index 13e0aac..7337dc1 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -270,7 +270,7 @@
 extern const struct of_device_id *of_match_node(
 	const struct of_device_id *matches, const struct device_node *node);
 extern int of_modalias_node(struct device_node *node, char *modalias, int len);
-extern struct device_node *of_parse_phandle(struct device_node *np,
+extern struct device_node *of_parse_phandle(const struct device_node *np,
 					    const char *phandle_name,
 					    int index);
 extern int of_parse_phandle_with_args(struct device_node *np,
@@ -438,7 +438,7 @@
 	return -ENOSYS;
 }
 
-static inline struct device_node *of_parse_phandle(struct device_node *np,
+static inline struct device_node *of_parse_phandle(const struct device_node *np,
 						   const char *phandle_name,
 						   int index)
 {