drm/omap: display: use devm_of_find_backlight

Look up backlight device using devm_of_find_backlight().
This simplifies the code and prevents us from hardcoding
the node name in the driver.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Zheng Bin <zhengbin13@huawei.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Enrico Weigelt <info@metux.net>
Cc: Allison Randal <allison@lohutok.net>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200514191001.457441-2-sam@ravnborg.org

drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c

@@ -1163,7 +1163,7 @@ static const struct omap_dss_driver dsicm_dss_driver = {
 static int dsicm_probe_of(struct platform_device *pdev)
 {
 	struct device_node *node = pdev->dev.of_node;
-	struct device_node *backlight;
+	struct backlight_device *backlight;
 	struct panel_drv_data *ddata = platform_get_drvdata(pdev);
 	struct display_timing timing;
 	int err;
@@ -1216,17 +1216,15 @@ static int dsicm_probe_of(struct platform_device *pdev)
 		ddata->vddi = NULL;
 	}
 
-	backlight = of_parse_phandle(node, "backlight", 0);
-	if (backlight) {
-		ddata->extbldev = of_find_backlight_by_node(backlight);
-		of_node_put(backlight);
+	backlight = devm_of_find_backlight(&pdev->dev);
+	if (IS_ERR(backlight))
+		return PTR_ERR(backlight);
 
-		if (!ddata->extbldev)
-			return -EPROBE_DEFER;
-	} else {
-		/* assume native backlight support */
+	/* If no backlight device is found assume native backlight support */
+	if (backlight)
+		ddata->extbldev = backlight;
+	else
 		ddata->use_dsi_backlight = true;
-	}
 
 	/* TODO: ulps */