s390/uvdevice: Add 'Lock Secret Store' UVC

Userspace can call the Lock Secret Store Ultravisor Call
using IOCTLs on the uvdevice. The Lock Secret Store UV call
disables all additions of secrets for the future.

The uvdevice is merely transporting the request from userspace to the
Ultravisor.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20230615100533.3996107-6-seiden@linux.ibm.com


Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Message-Id: <20230615100533.3996107-6-seiden@linux.ibm.com>