MINOR: cpu-topo: update CPU topology from excluded CPUs at boot

MINOR: cpu-topo: update CPU topology from excluded CPUs at boot

Now before trying to resolve the thread assignment to groups, we detect
which CPUs are not bound at boot so that we can mark them with
HA_CPU_F_EXCLUDED. This will be useful to better know on which CPUs we
can count later. Note that we purposely ignore cpu-map here as we
don't know how threads and groups will map to cpu-map entries, hence
which CPUs will really be used.

It's important to proceed this way so that when we have no info we
assume they're all available.