qemu: Split machine_ppc.py acceptance tests

qemu: Split machine_ppc.py acceptance tests

machine_ppc.py contains tests for 3 different ppc based machine types.  It
is listed in MAINTAINERS along with the PPC TCG cpu code.  That's not
really accurate though, since it's really more about testing those machines
than the CPUs.

Therefore, split it up into separate files for the separate machine types,
and list those along with their machine types in MAINTAINERS.

Suggested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210927044808.73391-2-david@gibson.dropbear.id.au>