drm/mediatek: convert dpi driver to use drm_of_find_panel_or_bridge

Convert dpi driver to use drm_of_find_panel_or_bridge.
This changes some error messages to debug messages (in the graph core).
Graph connections are often "no connects" depending on the particular
board, so we want to avoid spurious messages. Plus the kernel is not a
DT validator.
related links:
[1] https://lkml.org/lkml/2017/2/3/716
[2] https://lkml.org/lkml/2017/2/3/719Signed-off-by: chunhui dai <chunhui.dai@mediatek.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>

drivers/gpu/drm/mediatek/mtk_dpi.c

@@ -14,6 +14,7 @@
 #include <drm/drmP.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_crtc_helper.h>
+#include <drm/drm_of.h>
 #include <linux/kernel.h>
 #include <linux/component.h>
 #include <linux/platform_device.h>
@@ -668,7 +669,6 @@ static int mtk_dpi_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct mtk_dpi *dpi;
 	struct resource *mem;
-	struct device_node *bridge_node;
 	int comp_id;
 	int ret;
 
@@ -714,16 +714,12 @@ static int mtk_dpi_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	bridge_node = of_graph_get_remote_node(dev->of_node, 0, 0);
-	if (!bridge_node)
-		return -ENODEV;
-
-	dev_info(dev, "Found bridge node: %pOF\n", bridge_node);
+	ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0,
+					  NULL, &dpi->bridge);
+	if (ret)
+		return ret;
 
-	dpi->bridge = of_drm_find_bridge(bridge_node);
-	of_node_put(bridge_node);
-	if (!dpi->bridge)
-		return -EPROBE_DEFER;
+	dev_info(dev, "Found bridge node: %pOF\n", dpi->bridge->of_node);
 
 	comp_id = mtk_ddp_comp_get_id(dev->of_node, MTK_DPI);
 	if (comp_id < 0) {