wifi: mt76: mt7996: use correct phy for background radar event

If driver directly uses the band_idx reported from the radar event to
access mt76_phy array, it will get the wrong phy for background radar.
Fix this by adjusting the statement.

Fixes: 98686cd2 ("wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices")
Signed-off-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7996/mcu.c

@@ -339,7 +339,11 @@ mt7996_mcu_rx_radar_detected(struct mt7996_dev *dev, struct sk_buff *skb)
 	if (r->band_idx >= ARRAY_SIZE(dev->mt76.phys))
 		return;
 
-	mphy = dev->mt76.phys[r->band_idx];
+	if (dev->rdd2_phy && r->band_idx == MT_RX_SEL2)
+		mphy = dev->rdd2_phy->mt76;
+	else
+		mphy = dev->mt76.phys[r->band_idx];
+
 	if (!mphy)
 		return;