spapr: Simplify error handling in spapr_cpu_core_realize()

spapr: Simplify error handling in spapr_cpu_core_realize()

As recommended in "qapi/error.h", add a bool return value to
spapr_realize_vcpu() and use it in spapr_cpu_core_realize()
in order to get rid of the error propagation overhead.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20200914123505.612812-12-groug@kaod.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>