v7 chagnes: * rebased to latest master * added support of VIRTIO_NET_F_SPEED_DUPLEX
v6 changes: * fix code style v5 changes: * fixed code style * fixed commit message and logging text v4 changes: * link_speed renamed to speed devarg * speed devarg is added to virtio-user driver v3 changes: * link_speed devarg is added to virtio documentation
