target-i386: Implement CPUID[0xB] (Extended Topology Enumeration)

target-i386: Implement CPUID[0xB] (Extended Topology Enumeration)

I looked at a dozen Intel CPU that have this CPUID and all of them
always had Core offset as 1 (a wasted bit when hyperthreading is
disabled) and Package offset at least 4 (wasted bits at <= 4 cores).

QEMU uses more compact IDs and it doesn't make much sense to change it
now.  I keep the SMT and Core sub-leaves even if there is just one
thread/core;  it makes the code simpler and there should be no harm.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>