s390x/sclp: Fixed the size of sccb and code parameter

The pointer to the SCCB should not be limited to 32 bits only.
In contrast to this, the command word parameter is only 32 bits
(the upper 32 bits should be ignored).

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
