s390/zcrypt: New config switch CONFIG_ZCRYPT_DEBUG

Introduce a new config switch CONFIG_ZCRYPT_DEBUG which
will be used to enable some features for debugging the
zcrypt device driver and ap bus system:

Another patch will use this for displaying ap card and
ap queue state information via sysfs attribute.

A furher patch will use this to enable some special
treatment for some fields of an crypto request to be able
to inject failures and so help debugging with regards
to handling of failures.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>