acpi_piix4: Add infrastructure to send CPU hot-plug GPE to guest
* introduce processor status bitmask visible to guest at 0xaf00 addr,
where ACPI asl code expects it
* set bit corresponding to APIC ID in processor status bitmask on
receiving CPU hot-plug notification
* trigger CPU hot-plug SCI, to notify guest about CPU hot-plug event
Signed-off-by: Igor Mammedov <imammedo@redhat.com> Signed-off-by: Andreas Färber <afaerber@suse.de>