KVM: ppc: combine booke_guest.c and booke_host.c

The division was somewhat artificial and cumbersome, and had no functional
benefit anyways: we can only guests built for the real host processor.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>