mt76: mt76u: check tx_status_data pointer in mt76u_tx_tasklet

New devices (e.g. mt7663u) do not rely on stats workqueue to load tx
statistics but will be reported by the firmware. Check tx_status_data
pointer in mt76u_tx_tasklet in order to reuse tx tasklet for new devices
Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -708,7 +708,8 @@ static void mt76u_tx_tasklet(unsigned long data)
 
 		mt76_txq_schedule(&dev->phy, i);
 
-		if (!test_and_set_bit(MT76_READING_STATS, &dev->phy.state))
+		if (dev->drv->tx_status_data &&
+		    !test_and_set_bit(MT76_READING_STATS, &dev->phy.state))
 			queue_work(dev->usb.stat_wq, &dev->usb.stat_work);
 		if (wake)
 			ieee80211_wake_queue(dev->hw, i);