- implements QEMU hardware part of memory hot unplug protocol
  described at "docs/spec/acpi_mem_hotplug.txt"
- handles memory remove notification event
- handles device eject notification
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NZhu Guihua <zhugh.fnst@cn.fujitsu.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>