tools/power turbostat: Support Elkhart Lake

From a turbostat point of view the Tremont-based Elkhart Lake
is very similar to Goldmont, reuse the code of Goldmont.

Elkhart Lake does not support 'group turbo limit counter'
nor C3, adjust the code accordingly.

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>