s390/zcrypt: code beautify

Code beautify by following most of the checkpatch suggestions:
 - SPDX license identifier line complains by checkpatch
 - missing space or newline complains by checkpatch
 - octal numbers for permssions complains by checkpatch
 - renaming of static sysfs functions complains by checkpatch
 - fix of block comment complains by checkpatch
 - fix printf like calls where function name instead of %s __func__
   was used
 - __packed instead of __attribute__((packed))
 - init to zero for static variables removed
 - use of DEVICE_ATTR_RO and DEVICE_ATTR_RW macros

No functional code changes or API changes!

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>