drivers/net/wan/hdlc_cisco: Add hard_header_len

This driver didn't set hard_header_len. This patch sets hard_header_len
for it according to its header_ops->create function.

This driver's header_ops->create function (cisco_hard_header) creates
a header of (struct hdlc_header), so hard_header_len should be set to
sizeof(struct hdlc_header).

Cc: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Acked-by: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/hdlc_cisco.c

@@ -370,6 +370,7 @@ static int cisco_ioctl(struct net_device *dev, struct ifreq *ifr)
 		memcpy(&state(hdlc)->settings, &new_settings, size);
 		spin_lock_init(&state(hdlc)->lock);
 		dev->header_ops = &cisco_header_ops;
+		dev->hard_header_len = sizeof(struct hdlc_header);
 		dev->type = ARPHRD_CISCO;
 		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		netif_dormant_on(dev);