drm/sun4i: Set device driver data at bind time for use in unbind

Our sun4i_drv_unbind gets the drm device using dev_get_drvdata.
However, that driver data is never set in sun4i_drv_bind.

Set it there to avoid getting a NULL pointer at unbind time.

Fixes: 9026e0d122 ("drm: Add Allwinner A10 Display Engine support")
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190418132727.5128-3-paul.kocialkowski@bootlin.com

drivers/gpu/drm/sun4i/sun4i_drv.c

@@ -86,6 +86,8 @@ static int sun4i_drv_bind(struct device *dev)
 		ret = -ENOMEM;
 		goto free_drm;
 	}
+
+	dev_set_drvdata(dev, drm);
 	drm->dev_private = drv;
 	INIT_LIST_HEAD(&drv->frontend_list);
 	INIT_LIST_HEAD(&drv->engine_list);