ACPI: TSC breaks atkbd suspend

TSC is used even on machines when CONFIG_X86_TSC is not set (X86_TSC
means _require_ TSC), but it is not properly disabled when it is
unusable, because ACPI code understood the config switch as "may use
TSC".

This actually fixes suspend problems on my x60.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Len Brown <len.brown@intel.com>