mt76: mt76x02: only reset beacon drift counter when enabling beacons

When the timer is already running, there is no need to reset the counter,
because the drift will remain the same.
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76x02_mac.c

@@ -1126,6 +1126,9 @@ void mt76x02_mac_set_beacon_enable(struct mt76x02_dev *dev,
 	else if (val)
 		skb = ieee80211_beacon_get(mt76_hw(dev), vif);
 
+	if (!dev->beacon_mask)
+		dev->tbtt_count = 0;
+
 	__mt76x02_mac_set_beacon_enable(dev, vif_idx, val, skb);
 
 	if (mt76_is_mmio(dev))

drivers/net/wireless/mediatek/mt76/mt76x02_util.c

@@ -713,7 +713,6 @@ void mt76x02_bss_info_changed(struct ieee80211_hw *hw,
 			       MT_BEACON_TIME_CFG_INTVAL,
 			       info->beacon_int << 4);
 		dev->beacon_int = info->beacon_int;
-		dev->tbtt_count = 0;
 	}
 
 	if (changed & BSS_CHANGED_BEACON_ENABLED)