s390/uvdevice: Add 'Add Secret' UVC

Userspace can call the Add Secret Ultravisor Call using IOCTLs on the
uvdevice. The Add Secret UV call sends an encrypted and
cryptographically verified request to the Ultravisor. The request
inserts a protected guest's secret into the Ultravisor for later use.

The uvdevice is merely transporting the request from userspace to the
Ultravisor. It's neither checking nor manipulating the request data.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20230615100533.3996107-4-seiden@linux.ibm.com


Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Message-Id: <20230615100533.3996107-4-seiden@linux.ibm.com>