olpc_battery: Fix endian neutral breakage for s16 values

When the driver was updated to be endian neutral (8e9c7716)
the signed part of the s16 values was lost.  This is because be16_to_cpu()
returns an unsigned value.  This patch casts the values back to a s16
number prior to the the implicit cast up to an int.
Signed-off-by: Richard A. Smith <richard@laptop.org>
Signed-off-by: Daniel Drake <dsd@laptop.org>
Cc: <stable@kernel.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

drivers/power/olpc_battery.c

@@ -271,14 +271,14 @@ static int olpc_bat_get_property(struct power_supply *psy,
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 9760L / 32;
+		val->intval = (s16)be16_to_cpu(ec_word) * 9760L / 32;
 		break;
 	case POWER_SUPPLY_PROP_CURRENT_AVG:
 		ret = olpc_ec_cmd(EC_BAT_CURRENT, NULL, 0, (void *)&ec_word, 2);
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 15625L / 120;
+		val->intval = (s16)be16_to_cpu(ec_word) * 15625L / 120;
 		break;
 	case POWER_SUPPLY_PROP_CAPACITY:
 		ret = olpc_ec_cmd(EC_BAT_SOC, NULL, 0, &ec_byte, 1);
@@ -299,7 +299,7 @@ static int olpc_bat_get_property(struct power_supply *psy,
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 100 / 256;
+		val->intval = (s16)be16_to_cpu(ec_word) * 100 / 256;
 		break;
 	case POWER_SUPPLY_PROP_TEMP_AMBIENT:
 		ret = olpc_ec_cmd(EC_AMB_TEMP, NULL, 0, (void *)&ec_word, 2);
@@ -313,7 +313,7 @@ static int olpc_bat_get_property(struct power_supply *psy,
 		if (ret)
 			return ret;
 
-		val->intval = (int)be16_to_cpu(ec_word) * 6250 / 15;
+		val->intval = (s16)be16_to_cpu(ec_word) * 6250 / 15;
 		break;
 	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
 		ret = olpc_ec_cmd(EC_BAT_SERIAL, NULL, 0, (void *)&ser_buf, 8);