[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/include/linux/skbuff.h b/include/linux/skbuff.h
index 32635c4..db10335 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1203,6 +1203,8 @@
 extern void	       skb_split(struct sk_buff *skb,
 				 struct sk_buff *skb1, const u32 len);
 
+extern void	       skb_release_data(struct sk_buff *skb);
+
 static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
 				       int len, void *buffer)
 {