[S390] ctc: kmalloc->kzalloc/casting cleanups.

A patch for the CTC / ESCON network driver.  Switch from kmalloc to kzalloc
when appropriate, remove some unnecessary kmalloc casts too.  Since I have no
s390 machine, I didn't compile it but I examined it carefully.

Signed-off-by: "Ahmed S. Darwish" <darwish.07@gmail.com>
Cc: Frank Pavlic <fpavlic@de.ibm.com>
Cc: Ursula Braun <braunu@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>