tools/power turbostat: calculate TSC frequency from CPUID(0x15) on SKL

turbostat --debug
...
CPUID(0x15): eax_crystal: 2 ebx_tsc: 100 ecx_crystal_hz: 0
TSC: 1200 MHz (24000000 Hz * 100 / 2 / 1000000)

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