x86/cpu: Add definitions for the Intel Hardware Feedback Interface

Add the CPUID feature bit and the model-specific registers needed to
identify and configure the Intel Hardware Feedback Interface.

Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>