tools/power turbostat: KNL workaround for %Busy and Avg_MHz

KNL increments APERF and MPERF every 1024 clocks.
This is compliant with the architecture specification,
which requires that only the ratio of APERF/MPERF need be valid.

However, turbostat takes advantage of the fact that these
two MSRs increment every un-halted clock
at the actual and base frequency:

AVG_MHz = APERF_delta/measurement_interval

%Busy = MPERF_delta/TSC_delta

This quirk is needed for these calculations to also work on KNL,
which would otherwise show a value 1024x smaller than expected.

Signed-off-by: Hubert Chrzaniuk <hubert.chrzaniuk@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>