netfilter: nf_tables: use hook state from xt_action_param structure

Don't copy relevant fields from hook state structure, instead use the
one that is already available in struct xt_action_param.

This patch also adds a set of new wrapper functions to fetch relevant
hook state structure fields.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nft_fib.c b/net/netfilter/nft_fib.c
index 4944a8b..249c9b80 100644
--- a/net/netfilter/nft_fib.c
+++ b/net/netfilter/nft_fib.c
@@ -144,7 +144,7 @@ void nft_fib_store_result(void *reg, enum nft_fib_result r,
 		*dreg = index;
 		break;
 	case NFT_FIB_RESULT_OIFNAME:
-		dev = dev_get_by_index_rcu(pkt->net, index);
+		dev = dev_get_by_index_rcu(nft_net(pkt), index);
 		strncpy(reg, dev ? dev->name : "", IFNAMSIZ);
 		break;
 	default: