This patch adds basic support for the NuBus bus. This is used by 680x0
Macintosh.

Co-developed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Thomas Huth <huth@tuxfamily.org>
Message-Id: <20191026164546.30020-8-laurent@vivier.eu>