tools/power/turbostat: Abstract TSC tweak support

On some models, the CPU base frequency is different from the TSC
frequency, and the aperf/mperf counters are running at CPU base
frequency instead of TSC frequency.

Abstract support for TSC tweak.

Given that tsc_tweak depends on base_hz, move the code to probe_bclk()
after base_hz is available.

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