vhost: add APIs for live migration
This patch adds APIs to enable live migration for non-builtin data paths.
At src side, last_avail/used_idx from the device need to be set into the
virtio_net structure, and the log_base and log_size from the virtio_net
structure need to be set into the device.
At dst side, last_avail/used_idx need to be read from the virtio_net
structure and set into the device.
Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>