pc-bios/s390-ccw: make checkpatch happy

Remove tabs, tweak whitespace and comments.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Eugene (jno) Dvurechenski <jno@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
