drm/panel: simple: Use dev_err_probe() to simplify code

In the probe path, dev_err() can be replaced with dev_err_probe()
which will check if error code is -EPROBE_DEFER and prints the
error name. It also sets the defer probe reason which can be
checked later through debugfs.

Signed-off-by: Yuan Can <yuancan@huawei.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220929015503.17301-3-yuancan@huawei.com

Author: Yuan Can

drivers/gpu/drm/panel/panel-simple.c

@@ -575,12 +575,9 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 
 	panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
 						     GPIOD_OUT_LOW);
-	if (IS_ERR(panel->enable_gpio)) {
-		err = PTR_ERR(panel->enable_gpio);
-		if (err != -EPROBE_DEFER)
-			dev_err(dev, "failed to request GPIO: %d\n", err);
-		return err;
-	}
+	if (IS_ERR(panel->enable_gpio))
+		return dev_err_probe(dev, PTR_ERR(panel->enable_gpio),
+				     "failed to request GPIO\n");
 
 	err = of_drm_get_panel_orientation(dev->of_node, &panel->orientation);
 	if (err) {