netfilter: nf_tables: get rid of possible_net_t from set and basechain

We can pass the netns pointer as parameter to the functions that need to
gain access to it. From basechains, I didn't find any client for this
field anymore so let's remove this too.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nft_lookup.c b/net/netfilter/nft_lookup.c
index b8d18f5..e164325 100644
--- a/net/netfilter/nft_lookup.c
+++ b/net/netfilter/nft_lookup.c
@@ -35,7 +35,7 @@
 	const struct nft_set_ext *ext;
 	bool found;
 
-	found = set->ops->lookup(set, &regs->data[priv->sreg], &ext) ^
+	found = set->ops->lookup(pkt->net, set, &regs->data[priv->sreg], &ext) ^
 		priv->invert;
 
 	if (!found) {