6lowpan: fix debugfs interface entry name

This patches moves the debugfs interface related register after
netdevice register. The function lowpan_dev_debugfs_init will use
"dev->name" which can be before register_netdevice a format string.
The function register_netdevice will evaluate the format string if
necessary and replace "dev->name" to the real interface name.
Reported-by: Lukasz Duda <lukasz.duda@nordicsemi.no>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Acked-by: Lukasz Duda <lukasz.duda@nordicsemi.no>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/6lowpan/core.c

@@ -29,13 +29,13 @@ int lowpan_register_netdevice(struct net_device *dev,
 
 	lowpan_priv(dev)->lltype = lltype;
 
-	ret = lowpan_dev_debugfs_init(dev);
+	ret = register_netdevice(dev);
 	if (ret < 0)
 		return ret;
 
-	ret = register_netdevice(dev);
+	ret = lowpan_dev_debugfs_init(dev);
 	if (ret < 0)
-		lowpan_dev_debugfs_exit(dev);
+		unregister_netdevice(dev);
 
 	return ret;
 }