net: make ip6tunnel_xmit definition conditional

Moving the caller of iptunnel_xmit_stats causes a build error in
randconfig builds that disable CONFIG_INET:

In file included from ../net/xfrm/xfrm_input.c:17:0:
../include/net/ip6_tunnel.h: In function 'ip6tunnel_xmit':
../include/net/ip6_tunnel.h:93:2: error: implicit declaration of function 'iptunnel_xmit_stats' [-Werror=implicit-function-declaration]
  iptunnel_xmit_stats(dev, pkt_len);

The reason is that the iptunnel_xmit_stats definition is hidden
inside #ifdef CONFIG_INET but the caller is not. We can change
one or the other to fix it, and this patch adds a second #ifdef
around ip6tunnel_xmit() to avoid seeing the invalid call.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 039f5062 ("ip_tunnel: Move stats update to iptunnel_xmit()")
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_tunnel.h

@@ -81,6 +81,7 @@ __u32 ip6_tnl_get_cap(struct ip6_tnl *t, const struct in6_addr *laddr,
 struct net *ip6_tnl_get_link_net(const struct net_device *dev);
 int ip6_tnl_get_iflink(const struct net_device *dev);
 
+#ifdef CONFIG_INET
 static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb,
 				  struct net_device *dev)
 {
@@ -93,3 +94,4 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb,
 	iptunnel_xmit_stats(dev, pkt_len);
 }
 #endif
+#endif