dt-bindings: gpio: fix gpio-hog example

Even if this is no yaml yet at least fix the example to be compliant to
later schema as e.g. found in gpio-pca95xx.yaml, fairchild,74hc595.yaml
and gpio/fsl-imx-gpio.yaml.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Author: ziswiler

Documentation/devicetree/bindings/gpio/gpio.txt

@@ -213,7 +213,7 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
 		gpio-controller;
 		#gpio-cells = <2>;
 
-		line_b {
+		line_b-hog {
 			gpio-hog;
 			gpios = <6 0>;
 			output-low;