virtio-net: fix the upper bound when trying to delete queues

Virtqueue were indexed from zero, so don't delete virtqueue whose
index is n->max_queues * 2 + 1.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: qemu-stable <qemu-stable@nongnu.org>
Signed-off-by: NJason Wang <jasowang@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/net/virtio-net.c

@@ -1309,7 +1309,7 @@ static void virtio_net_set_multiqueue(VirtIONet *n, int multiqueue)
 
     n->multiqueue = multiqueue;
 
-    for (i = 2; i <= n->max_queues * 2 + 1; i++) {
+    for (i = 2; i < n->max_queues * 2 + 1; i++) {
         virtio_del_queue(vdev, i);
     }