mt76: mac: run mt76x02_mac_work routine atomically

Grab mt76_dev mutex in mt76x02_mac_work handler since it runs
concurrently with mt76x{0,2}_set_channel routines

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>

mt76x02_mac.c

@@ -779,6 +779,8 @@ void mt76x02_mac_work(struct work_struct *work)
 					       mac_work.work);
 	int i, idx;
 
+	mutex_lock(&dev->mt76.mutex);
+
 	mt76x02_update_channel(&dev->mt76);
 	for (i = 0, idx = 0; i < 16; i++) {
 		u32 val = mt76_rr(dev, MT_TX_AGG_CNT(i));
@@ -791,6 +793,8 @@ void mt76x02_mac_work(struct work_struct *work)
 	if (!dev->beacon_mask)
 		mt76x02_check_mac_err(dev);
 
+	mutex_unlock(&dev->mt76.mutex);
+
 	mt76_tx_status_check(&dev->mt76, NULL, false);
 
 	ieee80211_queue_delayed_work(mt76_hw(dev), &dev->mac_work,