pc-dimm: Fail realization for invalid nodes in non-NUMA config

pc_dimm_realize() validates the NUMA node to which memory hotplug is
being performed only in case of NUMA configuration. Include a check to
fail for invalid nodes in case of non-NUMA configuration too.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
