power: supply: max17047_battery: The temp alert values are 8-bit 2's complement

The temp alert values are 8-bit 2's complement, so sign-extend them
before reporting them back to the caller.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

drivers/power/supply/max17042_battery.c

@@ -270,14 +270,14 @@ static int max17042_get_property(struct power_supply *psy,
 		if (ret < 0)
 			return ret;
 		/* LSB is Alert Minimum. In deci-centigrade */
-		val->intval = (data & 0xff) * 10;
+		val->intval = sign_extend32(data & 0xff, 7) * 10;
 		break;
 	case POWER_SUPPLY_PROP_TEMP_ALERT_MAX:
 		ret = regmap_read(map, MAX17042_TALRT_Th, &data);
 		if (ret < 0)
 			return ret;
 		/* MSB is Alert Maximum. In deci-centigrade */
-		val->intval = (data >> 8) * 10;
+		val->intval = sign_extend32(data >> 8, 7) * 10;
 		break;
 	case POWER_SUPPLY_PROP_TEMP_MIN:
 		val->intval = chip->pdata->temp_min;