m48t59: introduce new base-year qdev property

m48t59: introduce new base-year qdev property

Currently the m48t59 device uses the hardware model in order to determine
whether the year value is offset from the hardware value. As this will
soon be required by the x59 model, create a qdev base-year property to
represent the base year and update the callers appropriately.

Reviewed-by: Hervé Poussineau <hpoussin@reactos.org>
CC: Andreas Färber <afaerber@suse.de>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>