bridge: use kobj_to_dev instead of to_dev

kobj_to_dev has been defined in linux/device.h, so I replace to_dev
with it.
Signed-off-by: NGeliang Tang <geliangtang@163.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/bridge/br_sysfs_br.c

@@ -22,7 +22,6 @@
 
 #include "br_private.h"
 
-#define to_dev(obj)	container_of(obj, struct device, kobj)
 #define to_bridge(cd)	((struct net_bridge *)netdev_priv(to_net_dev(cd)))
 
 /*
@@ -814,7 +813,7 @@ static ssize_t brforward_read(struct file *filp, struct kobject *kobj,
 			      struct bin_attribute *bin_attr,
 			      char *buf, loff_t off, size_t count)
 {
-	struct device *dev = to_dev(kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct net_bridge *br = to_bridge(dev);
 	int n;