create sysfs link from acpi device to sysdev for cpu

Sys I/F under acpi device node and sysdev device node are both
needed for cpu hot-removal. User space need this link so that
they know they are poking the sys I/F for the same cpu.
http://bugzilla.kernel.org/show_bug.cgi?id=9772



Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>