s390/ap/zcrypt: Revisit module param permissions

s390/ap/zcrypt: Revisit module param permissions

Revisit and rework module parameter permissions for AP bus and zcrypt
device drivers.

In general all sysfs permissions for AP bus and zcrypt parameters should be
0444 so that user space tools like lszcrypt can read the current value of
module parameters.

Some exceptions are only for some internal tweak parameters like
ap_msg_pool_min_items and zcrypt_mempool_threshold which should only be
readable by an administrator.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>