s390/zcrypt: harmonize debug feature calls and defines

This patch harmonizes the calls and defines around the
s390 debug feature as it is used in the AP bus and
zcrypt device driver code.

More or less cleanup and renaming, no functional changes.

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>