tools/power turbostat: save original CPU model

CPU model may get changed in intel_model_duplicates() for code reuse.
But there are still some cases we need the original CPU model to handle
minor differences between generations.

Thus save the original CPU model.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>