[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/skbuff.h b/include/linux/skbuff.h
index 0bedf53..3724790 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -90,7 +90,6 @@
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 struct nf_conntrack {
 	atomic_t use;
-	void (*destroy)(struct nf_conntrack *);
 };
 #endif
 
@@ -1556,10 +1555,11 @@
 }
 
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+extern void nf_conntrack_destroy(struct nf_conntrack *nfct);
 static inline void nf_conntrack_put(struct nf_conntrack *nfct)
 {
 	if (nfct && atomic_dec_and_test(&nfct->use))
-		nfct->destroy(nfct);
+		nf_conntrack_destroy(nfct);
 }
 static inline void nf_conntrack_get(struct nf_conntrack *nfct)
 {