power_supply: Move of_node out of the #ifdef CONFIG_OF

Similar to linux/device.h, move of_node struct member out of the #ifdef
CONFIG_OF so that the drivers won't have to mess with #ifdefs in .c files.
Signed-off-by: Anton Vorontsov <anton@enomsg.org>

include/linux/power_supply.h

@@ -162,6 +162,8 @@ union power_supply_propval {
 	const char *strval;
 };
 
+struct device_node;
+
 struct power_supply {
 	const char *name;
 	enum power_supply_type type;
@@ -173,9 +175,7 @@ struct power_supply {
 
 	char **supplied_from;
 	size_t num_supplies;
-#ifdef CONFIG_OF
 	struct device_node *of_node;
-#endif
 
 	int (*get_property)(struct power_supply *psy,
 			    enum power_supply_property psp,