virtio_ring: fix complaint by sparse

# make C=2 CF="-D__CHECK_ENDIAN__" ./drivers/virtio/

drivers/virtio/virtio_ring.c:423:19: warning: incorrect type in assignment (different base types)
drivers/virtio/virtio_ring.c:423:19: expected unsigned int [unsigned] [assigned] i
drivers/virtio/virtio_ring.c:423:19: got restricted __virtio16 [usertype] next
drivers/virtio/virtio_ring.c:423:19: warning: incorrect type in assignment (different base types)
drivers/virtio/virtio_ring.c:423:19: expected unsigned int [unsigned] [assigned] i
drivers/virtio/virtio_ring.c:423:19: got restricted __virtio16 [usertype] next
drivers/virtio/virtio_ring.c:423:19: warning: incorrect type in assignment (different base types)
drivers/virtio/virtio_ring.c:423:19: expected unsigned int [unsigned] [assigned] i
drivers/virtio/virtio_ring.c:423:19: got restricted __virtio16 [usertype] next
drivers/virtio/virtio_ring.c:604:39: warning: incorrect type in initializer (different base types)
drivers/virtio/virtio_ring.c:604:39: expected unsigned short [unsigned] [usertype] nextflag
drivers/virtio/virtio_ring.c:604:39: got restricted __virtio16
drivers/virtio/virtio_ring.c:612:33: warning: restricted __virtio16 degrades to integer

Signed-off-by: Gonglei <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>

drivers/virtio/virtio_ring.c

···
 		if (i == err_idx)
 			break;
 		vring_unmap_one(vq, &desc[i]);
-		i = vq->vring.desc[i].next;
+		i = virtio16_to_cpu(_vq->vdev, vq->vring.desc[i].next);
 	}
 
 	vq->vq.num_free += total_sg;
···
 static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
 {
 	unsigned int i, j;
-	u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
+	__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
 
 	/* Clear data ptr. */
 	vq->desc_state[head].data = NULL;