hw/s390x/ipl: Fix crash with virtio-scsi-pci device

qemu-system-s390x currently crashes when it is started with a
virtio-scsi-pci device, e.g.:

 qemu-system-s390x -nographic -enable-kvm -device virtio-scsi-pci \
                   -drive file=/tmp/disk.dat,if=none,id=d1,format=raw \
                   -device scsi-cd,drive=d1,bootindex=1

The problem is that the code in s390_gen_initial_iplb() currently assumes
that all SCSI devices are also CCW devices, which is not the case for
virtio-scsi-pci of course. Fix it by adding an appropriate check for
TYPE_CCW_DEVICE here.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <1493126327-13162-1-git-send-email-thuth@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
