The heathrow PIC is located within the macio device on real hardware so make it
a child of the macio-oldworld device. This also removes the need for setting and
checking a separate PIC object property link on the macio-oldworld device which
currently causes the automated QOM introspection tests to fail.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20201229175619.6051-4-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>