batman-adv: Rewrite debugfs kobj_to_* helpers as functions

CodingStyle "Chapter 12: Macros, Enums and RTL" highly recommends to use
functions instead of macros were possible. This ensures type safety and
prevents shadowing of other variables.
Signed-off-by: Sven Eckelmann <sven@narfation.org>

net/batman-adv/bat_sysfs.c

@@ -28,9 +28,17 @@
 #include "gateway_client.h"
 #include "vis.h"
 
-#define to_dev(obj)		container_of(obj, struct device, kobj)
-#define kobj_to_netdev(obj)	to_net_dev(to_dev(obj->parent))
-#define kobj_to_batpriv(obj)	netdev_priv(kobj_to_netdev(obj))
+static struct net_device *kobj_to_netdev(struct kobject *obj)
+{
+	struct device *dev = container_of(obj->parent, struct device, kobj);
+	return to_net_dev(dev);
+}
+
+static struct bat_priv *kobj_to_batpriv(struct kobject *obj)
+{
+	struct net_device *net_dev = kobj_to_netdev(obj);
+	return netdev_priv(net_dev);
+}
 
 /* Use this, if you have customized show and store functions */
 #define BAT_ATTR(_name, _mode, _show, _store)	\