led: gpio: Check device compatible string to determine the top level node

Since 2d1deaf88ed ("led: gpio: Drop duplicate OF "label" property parsing"),
all LED nodes have some sort of label. Use device_is_compatible(..."leds-gpio")
to determine whether this is a top-level node, since it is only the top
level node which is compatible with "leds-gpio", the GPIO LEDs subnodes
are not.

Fixes: 2d1deaf88ed ("led: gpio: Drop duplicate OF "label" property parsing")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Cc: Sean Anderson <seanga2@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Steven Lawrance <steven.lawrance@softathome.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Tested-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/drivers/led/led_gpio.c b/drivers/led/led_gpio.c
index 958dbd3..2315690 100644
--- a/drivers/led/led_gpio.c
+++ b/drivers/led/led_gpio.c
@@ -57,12 +57,11 @@
 
 static int led_gpio_probe(struct udevice *dev)
 {
-	struct led_uc_plat *uc_plat = dev_get_uclass_plat(dev);
 	struct led_gpio_priv *priv = dev_get_priv(dev);
 	int ret;
 
 	/* Ignore the top-level LED node */
-	if (!uc_plat->label)
+	if (device_is_compatible(dev, "gpio-leds"))
 		return 0;
 
 	ret = gpio_request_by_name(dev, "gpios", 0, &priv->gpio, GPIOD_IS_OUT);