pnv_core: drop reference on ICPState object during CPU realization

pnv_core: drop reference on ICPState object during CPU realization

Similarly to what was done to spapr with commit 249127d0dfeb, this patch
ensures that we don't keep an extra reference on the ICPState object. Also
since the object was just created and not reparented yet, the call to
object_property_add_child() should never fail: let's pass &error_abort to
make this clear.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>