mac80211: fix tx sequence number assignment with software queue + fast-xmit

When using software queueing, tx sequence number assignment happens at
ieee80211_tx_dequeue time, so the fast-xmit codepath must not do that.
Signed-off-by: NFelix Fietkau <nbd@openwrt.org>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -2767,7 +2767,8 @@ static bool ieee80211_xmit_fast(struct ieee80211_sub_if_data *sdata,
 
 	if (hdr->frame_control & cpu_to_le16(IEEE80211_STYPE_QOS_DATA)) {
 		*ieee80211_get_qos_ctl(hdr) = tid;
-		hdr->seq_ctrl = ieee80211_tx_next_seq(sta, tid);
+		if (!sta->sta.txq[0])
+			hdr->seq_ctrl = ieee80211_tx_next_seq(sta, tid);
 	} else {
 		info->flags |= IEEE80211_TX_CTL_ASSIGN_SEQ;
 		hdr->seq_ctrl = cpu_to_le16(sdata->sequence_number);