[NET]: Kill dead externs in netdevice.h

The following definitions are historical relics.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -923,8 +923,6 @@ extern void		dev_load(const char *name);
 extern void		dev_mcast_init(void);
 extern int		netdev_max_backlog;
 extern int		weight_p;
-extern unsigned long	netdev_fc_xoff;
-extern atomic_t netdev_dropping;
 extern int		netdev_set_master(struct net_device *dev, struct net_device *master);
 extern int skb_checksum_help(struct sk_buff *skb, int inward);
 /* rx skb timestamps */