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

This reverts commit 923b2e30.

This is not a correct fix as TCA_EXT_WARN_MSG is not a hierarchy to
TCA_ACT_TAB. I didn't notice the TC actions use different enum when adding
TCA_EXT_WARN_MSG. To fix the difference I will add a new WARN enum in
TCA_ROOT_MAX as Jamal suggested.
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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;