drm: bridge: Link encoder and bridge in core code

Instead of linking encoders and bridges in every driver (and getting it
wrong half of the time, as many drivers forget to set the drm_bridge
encoder pointer), do so in core code. The drm_bridge_attach() function
needs the encoder and optional previous bridge to perform that task,
update all the callers.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Stefan Agner <stefan@agner.ch> # For DCU
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com> # For atmel-hlcdc
Acked-by: Vincent Abriou <vincent.abriou@st.com> # For STI
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> # For sun4i
Acked-by: Xinliang Liu <z.liuxinliang@hisilicon.com> # For hisilicon
Acked-by: Jyri Sarha <jsarha@ti.com> # For tilcdc
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1481709550-29226-4-git-send-email-laurent.pinchart+renesas@ideasonboard.com

drivers/gpu/drm/mediatek/mtk_dpi.c

@@ -63,6 +63,7 @@ enum mtk_dpi_out_color_format {
 struct mtk_dpi {
 	struct mtk_ddp_comp ddp_comp;
 	struct drm_encoder encoder;
+	struct drm_bridge *bridge;
 	void __iomem *regs;
 	struct device *dev;
 	struct clk *engine_clk;
@@ -620,8 +621,7 @@ static int mtk_dpi_bind(struct device *dev, struct device *master, void *data)
 	/* Currently DPI0 is fixed to be driven by OVL1 */
 	dpi->encoder.possible_crtcs = BIT(1);
 
-	dpi->encoder.bridge->encoder = &dpi->encoder;
-	ret = drm_bridge_attach(dpi->encoder.dev, dpi->encoder.bridge);
+	ret = drm_bridge_attach(&dpi->encoder, dpi->bridge, NULL);
 	if (ret) {
 		dev_err(dev, "Failed to attach bridge: %d\n", ret);
 		goto err_cleanup;
@@ -718,9 +718,9 @@ static int mtk_dpi_probe(struct platform_device *pdev)
 
 	dev_info(dev, "Found bridge node: %s\n", bridge_node->full_name);
 
-	dpi->encoder.bridge = of_drm_find_bridge(bridge_node);
+	dpi->bridge = of_drm_find_bridge(bridge_node);
 	of_node_put(bridge_node);
-	if (!dpi->encoder.bridge)
+	if (!dpi->bridge)
 		return -EPROBE_DEFER;
 
 	comp_id = mtk_ddp_comp_get_id(dev->of_node, MTK_DPI);