ACPI battery: update status upon sysfs query

Sometimes the Battery driver doesn't get notifications when it's
plugged/unplugged. And this results in the incorrect Battery
status reported by the power supply sysfs I/F.

Update Battery status first when querying from sysfs.
http://marc.info/?l=linux-acpi&m=128855015826728&w=2

Tested_by: Seblu <seblu@seblu.net>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/battery.c

@@ -130,6 +130,8 @@ struct acpi_battery {
 	unsigned long flags;
 };
 
+static int acpi_battery_update(struct acpi_battery *battery);
+
 #define to_acpi_battery(x) container_of(x, struct acpi_battery, bat);
 
 inline int acpi_battery_present(struct acpi_battery *battery)
@@ -184,6 +186,9 @@ static int acpi_battery_get_property(struct power_supply *psy,
 	int ret = 0;
 	struct acpi_battery *battery = to_acpi_battery(psy);
 
+	if (acpi_battery_update(battery))
+		return -ENODEV;
+
 	if (acpi_battery_present(battery)) {
 		/* run battery update only if it is present */
 		acpi_battery_get_state(battery);