s390/zcrypt: use kzalloc

This patch fixes below warning reported by coccicheck

drivers/s390/crypto/zcrypt_ep11misc.c:198:8-15: WARNING:
kzalloc should be used for cprb, instead of kmalloc/memset

Link: https://lkml.kernel.org/r/1587472548-105240-1-git-send-email-zou_wei@huawei.com


Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>