ppc: spapr: Move VCPU ID calculation into sPAPR

ppc: spapr: Move VCPU ID calculation into sPAPR

Move the calculation of a CPU's VCPU ID out of the generic PPC code
(ppc_cpu_realizefn()) and into sPAPR specific code
(spapr_cpu_core_realize()) where it belongs.

Unfortunately, due to the way things are ordered, we still need to
default the VCPU ID in ppc_cpu_realizfn() but at least doing that
doesn't require any interaction with sPAPR.

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>