cpufreq: intel_pstate: Add Knights Mill CPUID

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

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