Please consider using __vring_new_virtqueue in mic_virtio

[Andy Lutomirski]

mic_virtio has a big hack to set up a custom ring, like this:

        /*
         * To reassign the used ring here we are directly accessing
         * struct vring_virtqueue which is a private data structure
         * in virtio_ring.c. At the minimum, a BUILD_BUG_ON() in
         * vring_new_virtqueue() would ensure that
         *  (&vq->vring == (struct vring *) (&vq->vq + 1));
         */
        vr = (struct vring *)(vq + 1);
        vr->used = used;\

I added a more flexible API __vring_new_virtqueue that you might be
able to use to clean this up in:

commit 2a2d1382fe9dccfce6f9c60a9c9fd2f0fe5bcf2b
Author: Andy Lutomirski <luto@xxxxxxxxxx>
Date:   Tue Feb 2 21:46:37 2016 -0800

    virtio: Add improved queue allocation API

Please consider either using it or trying to use
vring_create_virtqueue and updating it to fit your needs if
appropriate.

I didn't btry to do it myself because I don't have the hardware.

Thanks,
Andy