[NETFILTER]: nf_conntrack: kill destroy() in struct nf_conntrack for diet

The destructor per conntrack is unnecessary, then this replaces it with
system wide destructor.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 4777f1b..10b5c62 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -393,6 +393,7 @@
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 extern void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *);
 extern void nf_ct_attach(struct sk_buff *, struct sk_buff *);
+extern void (*nf_ct_destroy)(struct nf_conntrack *);
 #else
 static inline void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) {}
 #endif