netfilter: nfq_ct_hook needs __rcu and __read_mostly

This removes some sparse warnings.
Reported-by: Fengguang Wu <wfg@linux.intel.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter.h

@@ -404,7 +404,7 @@ struct nfq_ct_hook {
 	void (*seq_adjust)(struct sk_buff *skb, struct nf_conn *ct,
 			   u32 ctinfo, int off);
 };
-extern struct nfq_ct_hook *nfq_ct_hook;
+extern struct nfq_ct_hook __rcu *nfq_ct_hook;
 #else
 static inline void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) {}
 #endif

net/netfilter/core.c

@@ -265,7 +265,7 @@ void nf_conntrack_destroy(struct nf_conntrack *nfct)
 }
 EXPORT_SYMBOL(nf_conntrack_destroy);
 
-struct nfq_ct_hook *nfq_ct_hook;
+struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
 EXPORT_SYMBOL_GPL(nfq_ct_hook);
 
 #endif /* CONFIG_NF_CONNTRACK */