arch_topology: Don't set cluster identifier as physical package identifier

Currently as we parse the CPU topology from /cpu-map node from the
device tree, we assign generated cluster count as the physical package
identifier for each CPU which is wrong.

The device tree bindings for CPU topology supports sockets to infer
the socket or physical package identifier for a given CPU. Since it is
fairly new and not support on most of the old and existing systems, we
can assume all such systems have single socket/physical package.

Fix the physical package identifier to 0 by removing the assignment of
cluster identifier to the same.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>