numa: make sure that all cpus have has_node_id set if numa is enabled

It fixes/add missing _PXM object for non mapped CPU (x86)
and missing fdt node (virt-arm).

It ensures that possible_cpus contains complete mapping if
numa is enabled by the time machine_init() is executed.

As result non completely mapped CPUs:
 1) appear in ACPI/fdt blobs
 2) QMP query-hotpluggable-cpus command shows bound nodes for such CPUs
 3) allows to drop checks for has_node_id in numa only code,
   reducing number of invariants incomplete mapping could produce
 4) moves fixup/implicit node init from runtime numa_cpu_pre_plug()
   (when CPU object is created) to machine_numa_finish_init() which
   helps to fix [1, 2] and make possible_cpus complete source
   of numa mapping available even before CPUs are created.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1496161442-96665-4-git-send-email-imammedo@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
