KVM: PPC: Add PVR/PIR init for E500

commit 513579e3 change the way
we emulate PVR/PIR,
which left PVR/PIR uninitialized on E500, and make guest puzzled.

Signed-off-by: Liu Yu <yu.liu@freescale.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>