package/qemu: add support for PPC970 processors
PPC970 processors are well supported by the QEMU pseries and macbook
machines. The latest debian 11 (big endian) runs with SMP. Re-add
support.
Fixes: efc67deef38c ("qemu: remove support for some PowerPC processors in host qemu")
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>