[ACPI] Fix the regression with c1_default_handler on some systems

where C-states come from FADT.

Thanks to Kevin Radloff for identifying the issue and
isolating it to exact line of code that is causing the issue.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>