s390x: cpumodel: FMT2 and FMT4 SCLP test

SCLP is also part of the cpumodel, so we need to make sure that the
features indicated via read info / read cpu info are correct.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>