wifi: mt76: mt76x0: fix oob access in mt76x0_phy_get_target_power

After 'commit ba45841c ("wifi: mt76: mt76x02: simplify struct
mt76x02_rate_power")', mt76x02 relies on ht[0-7] rate_power data for
vht mcs{0,7}, while it uses vth[0-1] rate_power for vht mcs {8,9}.
Fix a possible out-of-bound access in mt76x0_phy_get_target_power routine.

Fixes: ba45841c ("wifi: mt76: mt76x02: simplify struct mt76x02_rate_power")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76x0/phy.c

@@ -642,7 +642,12 @@ mt76x0_phy_get_target_power(struct mt76x02_dev *dev, u8 tx_mode,
 		if (tx_rate > 9)
 			return -EINVAL;
 
-		*target_power = cur_power + dev->rate_power.vht[tx_rate];
+		*target_power = cur_power;
+		if (tx_rate > 7)
+			*target_power += dev->rate_power.vht[tx_rate - 8];
+		else
+			*target_power += dev->rate_power.ht[tx_rate];
+
 		*target_pa_power = mt76x0_phy_get_rf_pa_mode(dev, 1, tx_rate);
 		break;
 	default: