s390/sclp: introduce check for SIE

This patch adds a way to check if the SIE with zArchitecture support is
available.

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>