hw/ppc: Add emulation of Genesi/bPlan Pegasos II

Add new machine called pegasos2 emulating the Genesi/bPlan Pegasos II,
a PowerPC board based on the Marvell MV64361 system controller and the
VIA VT8231 integrated south bridge/superio chips. It can run Linux,
AmigaOS and a wide range of MorphOS versions. Currently a firmware ROM
image is needed to boot and only MorphOS has a video driver to produce
graphics output. Linux could work too but distros that supported this
machine don't include usual video drivers so those only run with
serial console for now.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <30cbfb9cbe6f46a1e15a69a75fac45ac39340122.1616680239.git.balaton@eik.bme.hu>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>