ACPI: battery: add sysfs serial number

egrep serial /proc/acpi/battery/BAT0/info
serial number:           32090

serial number can tell you from the imminent danger
of beeing set on fire.

Signed-off-by: maximilian attems <max@stro.at>
Acked-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index 5cbf3e3..68ed19c 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -94,6 +94,7 @@
 	/* Properties of type `const char *' */
 	POWER_SUPPLY_PROP_MODEL_NAME,
 	POWER_SUPPLY_PROP_MANUFACTURER,
+	POWER_SUPPLY_PROP_SERIAL_NUMBER,
 };
 
 enum power_supply_type {