powercap / RAPL: Add Knights Mill CPUID

Add Knights Mill (KNM) to the list of CPUIDs supported by intel_rapl

Signed-off-by: Piotr Luc <piotr.luc@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>