pseries: Fix compat_pvr on reset

pseries: Fix compat_pvr on reset

If we a migrate P8 machine to a P9 machine, the migration fails on
destination with:

  error while loading state for instance 0x1 of device 'cpu'
  load of migration failed: Operation not permitted

This is caused because the compat_pvr field is only present for the first
CPU.
Originally, spapr_machine_reset() calls ppc_set_compat() to set the value
max_compat_pvr for the first cpu and this was propagated to all CPUs by
spapr_cpu_reset().  Now, as spapr_cpu_reset() is called before that, the
value is not propagated to all CPUs and the migration fails.

To fix that, propagate the new value to all CPUs in spapr_machine_reset().

Fixes: 25c9780d38d4 ("spapr: Reset CAS & IRQ subsystem after devices")
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20190826090812.19080-1-lvivier@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>