netfilter: remove hook_entries field from nf_hook_state

This field is only useful for nf_queue, so store it in the
nf_queue_entry structure instead, away from the core path. Pass
hook_head to nf_hook_slow().

Since we always have a valid entry on the first iteration in
nf_iterate(), we can use 'do { ... } while (entry)' loop instead.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_queue.h

@@ -12,6 +12,7 @@ struct nf_queue_entry {
 	unsigned int		id;
 
 	struct nf_hook_state	state;
+	struct nf_hook_entry	*hook;
 	u16			size; /* sizeof(entry) + saved route keys */
 
 	/* extra space to store route keys */