intel_idle: Add support for the Airmont Core in the Cherrytrail and Braswell SOCs

Support C-states for the Airmont core in the Cherrytrail and Braswell SOCs.
The states are similar to those of Silvermont in Baytrail,
except both flavors of C6 states are faster.

Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Kumar P Mahesh <mahesh.kumar.p@intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>