s390/sclp: add detection of IPL-complete-control facility

The presence of the IPL-complete-control facility can be derived
from the hypervisor's SCLP info response.

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>