virtio-blk: Fix memleak on exit

Calling virtio_cleanup() will free up memory allocated in
virtio_common_init().

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 6471ac8..836dbc3 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -594,4 +594,5 @@
 {
     VirtIOBlock *s = to_virtio_blk(vdev);
     unregister_savevm(s->qdev, "virtio-blk", s);
+    virtio_cleanup(vdev);
 }