mt76: wait for pending tx to complete before switching channel

Reduces interruption caused by scanning

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/mediatek/mt76/dma.c

@@ -178,6 +178,10 @@ mt76_dma_tx_cleanup(struct mt76_dev *dev, enum mt76_txq_id qid, bool flush)
 		mt76_dma_sync_idx(dev, q);
 
 	wake = wake && qid < IEEE80211_NUM_ACS && q->queued < q->ndesc - 8;
+
+	if (!q->queued)
+		wake_up(&dev->tx_wait);
+
 	spin_unlock_bh(&q->lock);
 
 	if (wake)