tools/power/turbostat: Abstract BCLK frequency support

tools/power/turbostat: Abstract BCLK frequency support

Abstract CPU base clock frequency support.

Note that bclk is used by
1. calculate base_hz using MSR_PLATFORM_INFO, which is guarded by
   probe_nhm_msrs().
2. dump MSR_PLATFORM_INFO and Turbo Ratio Limit MSRs, which are also
   guarded by probe_nhm_msrs().
Thus probe_bclk() works for probe_nhm_msrs() models only.

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