ACPI / battery: Fix parsing _BIX return value

The _BIX method returns extended battery info as a package.
According the ACPI spec (ACPI 5, Section 10.2.2.2), the first member
of that package should be "Revision".  However, the current ACPI
battery driver treats the first member as "Power Unit" which should
be the second member.  This causes the result of _BIX return data
parsing to be incorrect.

Fix this by adding a new member called 'revision' to struct
acpi_battery and adding the offsetof() information on it to
extended_info_offsets[] as the first row.

[rjw: Changelog]
Reported-and-tested-by: Jan Hoffmann <jan.christian.hoffmann@gmail.com>
References: http://bugzilla.kernel.org/show_bug.cgi?id=60519
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Cc: 2.6.34+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/battery.c

@@ -117,6 +117,7 @@ struct acpi_battery {
 	struct acpi_device *device;
 	struct notifier_block pm_nb;
 	unsigned long update_time;
+	int revision;
 	int rate_now;
 	int capacity_now;
 	int voltage_now;
@@ -359,6 +360,7 @@ static struct acpi_offsets info_offsets[] = {
 };
 
 static struct acpi_offsets extended_info_offsets[] = {
+	{offsetof(struct acpi_battery, revision), 0},
 	{offsetof(struct acpi_battery, power_unit), 0},
 	{offsetof(struct acpi_battery, design_capacity), 0},
 	{offsetof(struct acpi_battery, full_charge_capacity), 0},