vhost-vdpa: introduce vhost-vdpa net client

vhost-vdpa: introduce vhost-vdpa net client

This patch set introduces a new net client type: vhost-vdpa.
vhost-vdpa net client will set up a vDPA device which is specified
by a "vhostdev" parameter.

Signed-off-by: Lingshan Zhu <[email protected]>
Signed-off-by: Tiwei Bie <[email protected]>
Signed-off-by: Cindy Lu <[email protected]>
Signed-off-by: Jason Wang <[email protected]>
Message-Id: <20200701145538[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Acked-by: Jason Wang <[email protected]>