ACPI: enable SMP C-states on x86_64

http://bugzilla.kernel.org/show_bug.cgi?id=5653



Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>