s390x: Return specification exception for unimplemented diag 308 subcodes

s390x: Return specification exception for unimplemented diag 308 subcodes

The architecture specifies specification exceptions for all
unavailable subcodes.

The presence of subcodes is indicated by checking some query subcode.
For example 6 will indicate that 3-6 are available. So future systems
might call new subcodes to check for new features. This should not
trigger a hw error, instead we return the architectured specification
exception.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Cc: qemu-stable@nongnu.org
Message-Id: <20190111113657.66195-3-frankja@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
(cherry picked from commit 37dbd1f4d4805edcd18d94eb202bb3461b3cd52d)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>