s390: Fix error handling and condition code of service call

Invalid sccb addresses will cause specification or addressing exception.
Lets add those checks. Furthermore, the good case (cc=0) was incorrect
for KVM, we did not set the CC at all. We now use return codes < 0
as program checks and return codes > 0 as condition code values.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
