libqos: fix typo in virtio.h QVirtQueue->used comment

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Tested-by: Eric Blake <eblake@redhat.com>
Tested-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20170628184724.21378-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/tests/libqos/virtio.h b/tests/libqos/virtio.h
index 3397a08..829de5e 100644
--- a/tests/libqos/virtio.h
+++ b/tests/libqos/virtio.h
@@ -26,7 +26,7 @@
 typedef struct QVirtQueue {
     uint64_t desc; /* This points to an array of struct vring_desc */
     uint64_t avail; /* This points to a struct vring_avail */
-    uint64_t used; /* This points to a struct vring_desc */
+    uint64_t used; /* This points to a struct vring_used */
     uint16_t index;
     uint32_t size;
     uint32_t free_head;