pc: migrate piix4 & ich9 MemHotplugState Adds an optional subsection that allows to migrate current state of acpi_memory_hotplug of ACPI PM device. Signed-off-by: Igor Mammedov <imammedo@redhat.com> Acked-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>