KVM: PPC: Booke-hv: Add one reg interface for SPRG9

We now support SPRG9 for guest, so also add a one reg interface for same
Note: Changes are in bookehv code only as we do not have SPRG9 on booke-pr.

Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>