drivers/vhost/vhost.c: delete double assignment

Delete successive assignments to the same location.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
expression i;
@@

*i = ...;
 i = ...;
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vhost.c

@@ -157,7 +157,6 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 	vq->avail_idx = 0;
 	vq->last_used_idx = 0;
 	vq->used_flags = 0;
-	vq->used_flags = 0;
 	vq->log_used = false;
 	vq->log_addr = -1ull;
 	vq->vhost_hlen = 0;