ACPI: CELSIUS_TO_KELVIN fixup

Fix an imprecision in CELSIUS_TO_KELVIN and move these
two macroes to a proper place.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Thomas Sujith <sujith.thomas@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>