tools/power turbostat: Add columns for clustered uncore frequency

New machines have multiple uncore frequencies per package,
visible in /sys/devices/system/cpu/intel_uncore_frequency/uncore##/

turbostat now samples these frequencies each measurement interval.

For each package, turbostat now prints "UMHzX.Y" columns,
where X = domain_id, and Y = fabric_cluster_id.

The system summary for each UMHzX.Y column is the average value
for across all of the packages in the system.

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