mac80211: add an optional TXQ for other PS-buffered frames

Some drivers may want to also use the TXQ abstraction with
non-data packets that need powersave buffering, so add a
hardware flag to allow this.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rx.c

@@ -1505,7 +1505,7 @@ static void sta_ps_start(struct sta_info *sta)
 	if (!sta->sta.txq[0])
 		return;
 
-	for (tid = 0; tid < ARRAY_SIZE(sta->sta.txq); tid++) {
+	for (tid = 0; tid < IEEE80211_NUM_TIDS; tid++) {
 		if (txq_has_queue(sta->sta.txq[tid]))
 			set_bit(tid, &sta->txq_buffered_tids);
 		else