netfilter: ip6tables regression fix

Commit 78454473 (netfilter: iptables: lock free counters) broke
ip6_tables by unconditionally returning ENOMEM in alloc_counters(),
Reported-by: NGraham Murray <graham@gmurray.org.uk>
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NPatrick McHardy <kaber@trash.net>

net/ipv6/netfilter/ip6_tables.c

@@ -1033,6 +1033,8 @@ static struct xt_counters *alloc_counters(struct xt_table *table)
 
 	xt_free_table_info(info);
 
+	return counters;
+
  free_counters:
 	vfree(counters);
  nomem: