KVM: s390: vsie: Make use of CRYCB FORMAT2 clear

The comment preceding the shadow_crycb function is
misleading, we effectively accept FORMAT2 CRYCB in the
guest.

When using FORMAT2 in the host we do not need to or with
FORMAT1.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180925231641.4954-18-akrowiak@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>