target-i386: Topology & APIC ID utility functions

target-i386: Topology & APIC ID utility functions

This introduces utility functions for the APIC ID calculation, based on:
  Intel® 64 Architecture Processor Topology Enumeration
  http://software.intel.com/en-us/articles/intel-64-architecture-processor-topology-enumeration/

The code should be compatible with AMD's "Extended Method" described at:
  AMD CPUID Specification (Publication #25481)
  Section 3: Multiple Core Calcuation
as long as:
 - nr_threads is set to 1;
 - OFFSET_IDX is assumed to be 0;
 - CPUID Fn8000_0008_ECX[ApicIdCoreIdSize[3:0]] is set to
   apicid_core_width().

Unit tests included.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>