s390/zcrypt: Removed unneeded debug feature directory creation.

The ap bus code and the zcrypt api had invocations to the
debug feature debugfs_create_dir() call but never populated
these directories in any way. Removed this unneeded code.

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