qemu: Parse CPU stepping from query-cpu-model-expansion

qemu: Parse CPU stepping from query-cpu-model-expansion

Even though only family and model are used for matching CPUID data with
CPU models from cpu_map.xml, stepping is used by x86DataFilterTSX which
is supposed to disable TSX on CPU models with broken TSX support. Thus
we need to start parsing stepping from QEMU to make sure we don't
disable TSX on CPUs which provide working TSX implementation. See the
following patch for a real world example of such CPU.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>