ACPI: Adjust Kelvin offset to match local implementation

The exact offset between Kelvin and degree Celsius is 273.15. However
ACPI handles temperature values with a single decimal place. As a
consequence, some implementations use an offset of 273.1 and others
use an offset of 273.2. Try to find out which one is being used, to
present the most accurate and visually appealing number.

Tested on a Sony Vaio PGC-GR214EP (which uses 273.1) and a Lenovo
Thinkpad T60p (which uses 273.2).

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>