ipack: Convert to QOM realize

Acked-by: Alberto Garcia <agarcia@igalia.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
ipack: QOM parent field cleanup for IPackBus

Clean up the only user of IPackBus::qbus field and rename it.

Acked-by: Alberto Garcia <agarcia@igalia.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
ipack: QOM parent field cleanup for IPackDevice

Rename the IPackDevice::qdev field to avoid accidental use.

Acked-by: Alberto Garcia <agarcia@igalia.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>