s390/zcrypt: Slight rework on the agent_id field

s390/zcrypt: Slight rework on the agent_id field

The agent_id field is a two byte ascii field addressing
the target agent on the crypto card. Some code however
addresses this field as unsigned short. Rework these
places to treat this field always as a two byte array.
Unfortunately this field also shows up as __u16 in
struct ica_xcRB as part of the zcrypt ioctl interface.
Leave this untouched as it would break the API.

There are two other places (func_id) where a byte array
gets assigned with hex values but in fact these are ascii
value. So replace these assignments with real ascii values
for more readability.

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