Functionally, this is a revert of Jocelyn's r3309 /
55aa45ddde (Quickly hack PowerPC BIOS
able to boot on CDROM again.), for which we do not have the sources.
Therefore the sources used are v0.4.1 plus pc-bios/ohw.diff plus a
workaround turning IDE errors into warnings.
Signed-off-by: Andreas Färber <andreas.faerber@web.de>