tools/power turbostat: decode Baytrail CC6 and MC6 demotion configuration

with --debug, see:

cpu0: MSR_CC6_DEMOTION_POLICY_CONFIG: 0x00000000 (DISable-CC6-Demotion)
cpu0: MSR_MC6_DEMOTION_POLICY_CONFIG: 0x00000000 (DISable-MC6-Demotion)

Note that the hardware default is to enable demotion,
and Linux started clearing these registers in 3.17.

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