s390/zcrypt: Provide target domain for EP11 cprbs to scheduling function

The scheduling function will get an extension which will
process the target_id value from an EP11 cprb. This patch
extracts the value during preparation of the ap message.

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