mt76: mt7615: fix monitor mode on second PHY

The second PHY receives no packets unless there is an active vif present.
Set the WANT_MONITOR_VIF flag to deal with that
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7615/init.c

@@ -415,6 +415,9 @@ int mt7615_register_ext_phy(struct mt7615_dev *dev)
 	mphy->sband_2g.sband.n_channels = 0;
 	mphy->hw->wiphy->bands[NL80211_BAND_2GHZ] = NULL;
 
+	/* The second interface does not get any packets unless it has a vif */
+	ieee80211_hw_set(mphy->hw, WANT_MONITOR_VIF);
+
 	ret = mt76_register_phy(mphy);
 	if (ret)
 		ieee80211_free_hw(mphy->hw);

drivers/net/wireless/mediatek/mt76/mt7615/main.c

@@ -177,9 +177,11 @@ static int mt7615_add_interface(struct ieee80211_hw *hw,
 			       MT_WTBL_UPDATE_ADM_COUNT_CLEAR);
 
 	rcu_assign_pointer(dev->mt76.wcid[idx], &mvif->sta.wcid);
-	mtxq = (struct mt76_txq *)vif->txq->drv_priv;
-	mtxq->wcid = &mvif->sta.wcid;
-	mt76_txq_init(&dev->mt76, vif->txq);
+	if (vif->txq) {
+		mtxq = (struct mt76_txq *)vif->txq->drv_priv;
+		mtxq->wcid = &mvif->sta.wcid;
+		mt76_txq_init(&dev->mt76, vif->txq);
+	}
 
 out:
 	mutex_unlock(&dev->mt76.mutex);
@@ -201,7 +203,8 @@ static void mt7615_remove_interface(struct ieee80211_hw *hw,
 	mt7615_mcu_set_dev_info(dev, vif, 0);
 
 	rcu_assign_pointer(dev->mt76.wcid[idx], NULL);
-	mt76_txq_remove(&dev->mt76, vif->txq);
+	if (vif->txq)
+		mt76_txq_remove(&dev->mt76, vif->txq);
 
 	mutex_lock(&dev->mt76.mutex);
 	dev->vif_mask &= ~BIT(mvif->idx);