net/sched: act_api: move TCA_EXT_WARN_MSG to the correct hierarchy

TCA_EXT_WARN_MSG is currently sitting outside of the expected hierarchy
for the tc actions code. It should sit within TCA_ACT_TAB.

Fixes: 0349b87 ("sched: add new attr TCA_EXT_WARN_MSG to report tc extact message")
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_api.c

@@ -1596,12 +1596,12 @@ static int tca_get_fill(struct sk_buff *skb, struct tc_action *actions[],
 	if (tcf_action_dump(skb, actions, bind, ref, false) < 0)
 		goto out_nlmsg_trim;
 
-	nla_nest_end(skb, nest);
-
 	if (extack && extack->_msg &&
 	    nla_put_string(skb, TCA_EXT_WARN_MSG, extack->_msg))
 		goto out_nlmsg_trim;
 
+	nla_nest_end(skb, nest);
+
 	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
 
 	return skb->len;