virtio-ccw/migration: Migrate config vector for virtio devices

virtio-ccw/migration: Migrate config vector for virtio devices

virtio_ccw_{save|load}_config are missing code to save and restore a vdev's
config_vector value. This causes some virtio devices to become disabled
following a migration.

This patch fixes a bug whereby the qmp/hmp balloon command (virsh setmem)
silently fails to update the guest's available memory because the device was not
properly migrated.

This will break compatibility, but vmstate_s390_cpu was bumped from
version 2 to version 4 between v2.3.0 and v2.4.0 without a compat
handler. Furthermore, there is no production environment yet so
migration is fenced anyway between any relevant version of 2.3 and 2.4.

Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Message-Id: <1433343843-803-1-git-send-email-jjherne@linux.vnet.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>