ACPI, APEI, Manage GHES as platform devices

Register GHES during HEST initialization as platform devices. And make
GHES driver into platform device driver. So that the GHES driver
module can be loaded automatically when there are GHES available.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>