gpio: fix description for gpio-ranges example

The length of the second entry is 20, so it affects GPIOs 10..29.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/gpio/gpio.txt

@@ -282,8 +282,8 @@ Example 1:
 	};
 
 Here, a single GPIO controller has GPIOs 0..9 routed to pin controller
-pinctrl1's pins 20..29, and GPIOs 10..19 routed to pin controller pinctrl2's
-pins 50..59.
+pinctrl1's pins 20..29, and GPIOs 10..29 routed to pin controller pinctrl2's
+pins 50..69.
 
 Example 2: