power: supply: core: add manufacture date properties

Some smart batteries store their manufacture date, which is
useful to identify the battery and/or to know about the cell
quality.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
index e664774..78d5382 100644
--- a/drivers/power/supply/power_supply_sysfs.c
+++ b/drivers/power/supply/power_supply_sysfs.c
@@ -198,6 +198,9 @@ static struct power_supply_attr power_supply_attrs[] = {
 	POWER_SUPPLY_ATTR(PRECHARGE_CURRENT),
 	POWER_SUPPLY_ATTR(CHARGE_TERM_CURRENT),
 	POWER_SUPPLY_ATTR(CALIBRATE),
+	POWER_SUPPLY_ATTR(MANUFACTURE_YEAR),
+	POWER_SUPPLY_ATTR(MANUFACTURE_MONTH),
+	POWER_SUPPLY_ATTR(MANUFACTURE_DAY),
 	/* Properties of type `const char *' */
 	POWER_SUPPLY_ATTR(MODEL_NAME),
 	POWER_SUPPLY_ATTR(MANUFACTURER),