s390/zcrypt: Move the ap bus into kernel

Move the ap bus into the kernel and make it general available.
Additionally include the message types and the API layer as a
preparation for the workload management facility.

Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>