wifi: mt76: connac: accept hw scan request at a time

The current hw scan cannot accept multiple hw scan requests at a time, we
return the proper error code when the hw scan is still undergoing.
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c

@@ -1571,6 +1571,9 @@ int mt76_connac_mcu_hw_scan(struct mt76_phy *phy, struct ieee80211_vif *vif,
 	struct mt76_connac_hw_scan_req *req;
 	struct sk_buff *skb;
 
+	if (test_bit(MT76_HW_SCANNING, &phy->state))
+		return -EBUSY;
+
 	skb = mt76_mcu_msg_alloc(mdev, NULL, sizeof(*req));
 	if (!skb)
 		return -ENOMEM;