Propagate the topology information from the PPTT tree to the
cpu_topology array. We can get the thread id, core_id and
cluster_id by assuming certain levels of the PPTT tree correspond
to those concepts. The package_id is flagged in the tree and can be
found by passing an arbitrary large level to setup_acpi_cpu_topology()
which terminates its search when it finds an ACPI node flagged
as the physical package. If the tree doesn't contain enough
levels to represent all of thread/core/cod/package then the package
id will be used for the missing levels.

Since server/ACPI machines are more likely to be multisocket and NUMA,
this patch also modifies the default clusters=sockets behavior
for ACPI machines to sockets=sockets. DT machines continue to
represent sockets as clusters. For ACPI machines, this results in a
more normalized view of the topology. Cluster level scheduler decisions
are still being made due to the "MC" level in the scheduler which has
know...