drm: add unique identifiers to dmabufs

src/compositor.rs

@@ -201,6 +201,7 @@ fn start_compositor2(
         default_gfx_api: Cell::new(GfxApi::OpenGl),
         activation_tokens: Default::default(),
         toplevel_lists: Default::default(),
+        dma_buf_ids: Default::default(),
     });
     state.tracker.register(ClientId::from_raw(0));
     create_dummy_output(&state);