lib: s390x: Add access key argument to tprot

Currently there is only one callee passing a non zero key,
but having the argument will be useful in the future.

Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/kvm/20211007085027.13050-1-frankja@linux.ibm.com/T/#md3064e13e876e0418a16f0d5a5bd9a6f2adebfd9


Signed-off-by: Janosch Frank <frankja@linux.ibm.com>