tools/power turbostat: Rename physical_core_id to core_id

tools/power turbostat: Rename physical_core_id to core_id

The Linux Kernel topology sysfs is flawed.
core_id is not globally unique, but is per-package.

Turbostat works around this when it needs to, with

        rapl_core_id = cpus[cpu].core_id;
        rapl_core_id += cpus[cpu].package_id * nr_cores_per_package

Otherwise, turbostat handles core_id as subservient to each package.

As there is only one core_id namespace, rename
physical_core_id to simply be core_id.

No functional change.

Signed-off-by: Len Brown <len.brown@intel.com>