s390x: skey: Test for ADDRESSING exceptions

... used to be broken in TCG, so let's add a very simple test for SSKE
and ISKE. In order to test RRBE as well, introduce a helper to call the
machine instruction.

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210903162537.57178-1-david@redhat.com>
Link: https://lore.kernel.org/kvm/20210903162537.57178-1-david@redhat.com/


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