virtio-net: support queue reset

virtio-net: support queue reset

virtio-net and vhost-kernel implement queue reset.
Queued packets in the corresponding queue pair are flushed
or purged.

For virtio-net, userspace datapath will be disabled later in
__virtio_queue_reset(). It will set addr of vring to 0 and idx to 0.
Thus, virtio_net_receive() and virtio_net_flush_tx() will not receive
or send packets.

For vhost-net, the datapath will be disabled in vhost_net_virtqueue_reset().

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20221017092558.111082-13-xuanzhuo@linux.alibaba.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>