ip_tunnel: Protect tunnel functions with CONFIG_INET guard.

Tunnel constants can be used in generic code but in these cases
the inline functions in ip_tunnels.h cause compilation problems
if CONFIG_INET is not set.

CC: Pravin Shelar <pshelar@nicira.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip_tunnels.h

@@ -93,6 +93,8 @@ struct ip_tunnel_net {
 	struct net_device *fb_tunnel_dev;
 };
 
+#ifdef CONFIG_INET
+
 int ip_tunnel_init(struct net_device *dev);
 void ip_tunnel_uninit(struct net_device *dev);
 void  ip_tunnel_dellink(struct net_device *dev, struct list_head *head);
@@ -180,4 +182,7 @@ static inline void iptunnel_xmit_stats(int err,
 		err_stats->tx_dropped++;
 	}
 }
+
+#endif /* CONFIG_INET */
+
 #endif /* __NET_IP_TUNNELS_H */