lib: s390x: sclp: Extend feature probing

Let's grab more of the feature bits from SCLP read info so we can use
them in the cpumodel tests.

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