vhost: remove avail_event arg from vhost_update_avail_event()

In vhost_update_avail_event() we never used the `avail_event` argument,
since its introduction in commit 2723feaa8ec6 ("vhost: set log when
updating used flags or avail event").

Let's remove it to clean up the code.

Signed-off-by: Stefano Garzarella <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Michael S. Tsirkin <[e-mail]>

drivers/vhost/vhost.c

···
 	return 0;
 }
 
-static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
+static int vhost_update_avail_event(struct vhost_virtqueue *vq)
 {
 	if (vhost_put_avail_event(vq))
 		return -EFAULT;
···
 			return false;
 		}
 	} else {
-		r = vhost_update_avail_event(vq, vq->avail_idx);
+		r = vhost_update_avail_event(vq);
 		if (r) {
 			vq_err(vq, "Failed to update avail event index at %p: %d\n",
 			       vhost_avail_event(vq), r);