s390/pkey: remove redundant variable initialization

In the first place, the initialization value of `rc` is wrong.
It is unnecessary to initialize `rc` variables, so remove their
initialization operation.

Fixes: f2bbc96e ("s390/pkey: add CCA AES cipher key support")
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>