net-sysfs: add a newline when printing 'tx_timeout' by sysfs

When I cat 'tx_timeout' by sysfs, it displays as follows. It's better to
add a newline for easy reading.

root@syzkaller:~# cat /sys/devices/virtual/net/lo/queues/tx-0/tx_timeout
0root@syzkaller:~#
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/net-sysfs.c

@@ -1108,7 +1108,7 @@ static ssize_t tx_timeout_show(struct netdev_queue *queue, char *buf)
 	trans_timeout = queue->trans_timeout;
 	spin_unlock_irq(&queue->_xmit_lock);
 
-	return sprintf(buf, "%lu", trans_timeout);
+	return sprintf(buf, fmt_ulong, trans_timeout);
 }
 
 static unsigned int get_netdev_queue_index(struct netdev_queue *queue)