s390/net: Cleanup claw printk messages.

Cc: Martin Schwidefsky <schwidefska@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NAndy Richter <richtera@us.ibm.com>
Signed-off-by: NUrsula Braun <ursula.braun@de.ibm.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>