spapr-cpu-core: Release ICPState object during CPU unrealization

Recent commits that re-organized ICPState object missed to destroy
the object when CPU is unrealized. Fix this so that CPU unplug
doesn't abort QEMU.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr_cpu_core.c

@@ -127,6 +127,7 @@ static void spapr_cpu_core_unrealizefn(DeviceState *dev, Error **errp)
         PowerPCCPU *cpu = POWERPC_CPU(cs);
 
         spapr_cpu_destroy(cpu);
+        object_unparent(cpu->intc);
         cpu_remove_sync(cs);
         object_unparent(obj);
     }