machine: Add helpers to get cores/threads per socket

machine: Add helpers to get cores/threads per socket

The number of cores/threads per socket are needed for smbios, and are
also useful for other modules.

Provide the helpers to wrap the calculation of cores/threads per socket
so that we can avoid calculation errors caused by other modules miss
topology changes.

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Message-Id: <20230628135437.1145805-2-zhao1.liu@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>