ACPI: processor: remove _PDC object list from struct acpi_processor

When we call _PDC, we get a handle to the processor, allocate the
object list buffer as needed, and free it immediately after calling
_PDC.

There's no need to drag around this object list with us everywhere
else, so let's just get rid of it.

Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>