tools/power turbostat: Skip printing disabled package C-states

Replaced previously open-coded Package C-state Limit decoding
with table-driven decoding.  In doing so, updated to match January 2015
"Intel(R) 64 and IA-23 Architectures Software Developer's Manual".

In the past, turbostat would print package C-state residency columns
for all package states supported by the model's architecture, even though
a particular SKU may not support them, or they may be disabled by the BIOS.
Now turbostat will skip printing colunns if MSRs indicate that they are not enabled.
eg. many SKUs don't support PC7, and so that column will no longer be printed.

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