tools / power turbostat: Support Silvermont

Support the next generation Intel Atom processor
mirco-architecture, formerly called Silvermont.

The server version, formerly called "Avoton",
is named the "Intel(R) Atom(TM) Processor C2000 Product Family".

The client version, formerly called "Bay Trail",
is named the "Intel Atom Processor Z3000 Series",
as well as various "Intel Pentium Processor"
and "Intel Celeron Processor" brands, depending
on form-factor.

Silvermont has a set of MSRs not far off from NHM,
but the RAPL register set is a sub-set of those previously supported.

Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>