s390x/sclpconsole: Remove dead code - remove exit handlers

The other event handlers (quiesce and cpu) do not define these
handlers, and this one does nothing, so it can be removed.

Signed-off-by: Nia Alarie <nia.alarie@gmail.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20180306100721.19419-1-nia.alarie@gmail.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>