i386: Add die-level cpu topology to x86CPU on PCMachine

i386: Add die-level cpu topology to x86CPU on PCMachine

The die-level as the first PC-specific cpu topology is added to the leagcy
cpu topology model, which has one die per package implicitly and only the
numbers of sockets/cores/threads are configurable.

In the new model with die-level support, the total number of logical
processors (including offline) on board will be calculated as:

     #cpus = #sockets * #dies * #cores * #threads

and considering compatibility, the default value for #dies would be
initialized to one in x86_cpu_initfn() and pc_machine_initfn().

Signed-off-by: Like Xu <like.xu@linux.intel.com>
Message-Id: <20190612084104.34984-2-like.xu@linux.intel.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>