s390/zcrypt_msgtype6: Cleanup debug code

The dynamic debugging provides function names on request. So remove
all explicit function strings.

Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
[dengler: fix indent]
Signed-off-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>