Revert "atm: Do not free already unregistered net device."

This reverts commit 65e41136.

Unlike the other cases Pavel fixed, this case did not
setup a netdev->destructor of free_netdev, therefore this
change was not correct.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/atm/br2684.c

@@ -350,6 +350,7 @@ static void br2684_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
 			list_del(&brdev->br2684_devs);
 			write_unlock_irq(&devs_lock);
 			unregister_netdev(net_dev);
+			free_netdev(net_dev);
 		}
 		return;
 	}
@@ -770,6 +771,7 @@ static void __exit br2684_exit(void)
 
 		list_del(&brdev->br2684_devs);
 		unregister_netdev(net_dev);
+		free_netdev(net_dev);
 	}
 }