s390: deprecate the non-ccw machine in 2.5

s390: deprecate the non-ccw machine in 2.5

The non-ccw machine for s390 (s390-virtio) is not very well maintained
and caused several issues in the past:
- aliases like virtio-blk did not work for s390
- virtio refactoring failed due to long standing bugs (e.g.see
commit cb927b8a "s390-virtio: Accommodate guests using virtqueues too early")
- some features like memory hotplug will cause trouble due to virtio storage
  being above guest memory
- the boot loader bios no longer seems to work. the source code of that
  loader is also no longer maintained

2.4 changed the default to the ccw machine, let's deprecate the old
machine for 2.5.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Message-Id: <1446811645-25565-1-git-send-email-borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>