target-ppc: KVMPPC_H_CAS fix cpu-version endianess

During KVMPPC_H_CAS processing, the cpu-version updated value is stored
without taking care of the current endianess. As a consequence, the guest
may not switch to the right CPU model, leading to unexpected results.

If needed, the value is now converted.

Fixes: 6d9412ea8132 ("target-ppc: Implement "compat" CPU option")
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
