Since commit dd3be74207 SUNW,fdtwo's
initfn (realizefn since 940194c236)
was using SYSBUS_FDC() cast. This uses type sysbus-fdc rather than
SUNW,fdtwo.
Fix this by letting SUNW,fdtwo and sysbus-fdc both inherit from an
abstract type base-sysbus-fdc.
This allows to consolidate realizefns by using instance_init functions.
Clean up variable names and variable order while at it.
Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: Hu Tao <hutao@cn.fujitsu.com>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Andreas Färber <afaerber@suse.de>