[NET]: Fix sparse warnings

Of this type, mostly:

CHECK   net/ipv6/netfilter.c
net/ipv6/netfilter.c:96:12: warning: symbol 'ipv6_netfilter_init' was not declared. Should it be static?
net/ipv6/netfilter.c:101:6: warning: symbol 'ipv6_netfilter_fini' was not declared. Should it be static?

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index e553e5b..c3123c9 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -770,7 +770,7 @@
 	return 0;
 }
 
-int __init ipip6_fb_tunnel_init(struct net_device *dev)
+static int __init ipip6_fb_tunnel_init(struct net_device *dev)
 {
 	struct ip_tunnel *tunnel = dev->priv;
 	struct iphdr *iph = &tunnel->parms.iph;