Instead of having the parent provide PITCommonClass::init,
let the children override DeviceClass::realize themselves.
This pushes the responsibility for saving and calling the parent's
realizefn to the children.
Signed-off-by: Andreas Färber <afaerber@suse.de>
Drop ISADeviceClass::init and the resulting no-op initfn and let
children implement their own realizefn. Adapt error handling.
Split off an instance_init where sensible.
Signed-off-by: Andreas Färber <afaerber@suse.de>