tun: drop TUN_DEBUG and tun_debug()

static void tun_default_link_ksettings(struct net_device *dev,

				       struct ethtool_link_ksettings *cmd);

/* Uncomment to enable debugging */

/* #define TUN_DEBUG 1 */

#ifdef TUN_DEBUG

#define tun_debug(level, tun, fmt, args...)			\

do {								\

	if (tun->msg_enable)					\

		netdev_printk(level, tun->dev, fmt, ##args);	\

} while (0)

#else

#define tun_debug(level, tun, fmt, args...)			\

do {								\

	if (0)							\

		netdev_printk(level, tun->dev, fmt, ##args);	\

} while (0)

#endif

#define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)

/* TUN device flags */