macio: don't reference serial_hd() directly within the device

Instead use qdev_prop_set_chr() to configure the ESCC serial chardevs at the
Mac Old World and New World machine level.

Also remove the now obsolete comment referring to the use of serial_hd() and
the setting of user_creatable to false accordingly.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20201013114922.2946-2-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
3 files changed