dt-bindings: i2c: at91: fix example for scl-gpios

The SCL gpio pin used by I2C bus for recovery needs to be configured as
open drain, so fix the binding example accordingly.
In relation with fix c5a28380 ("ARM: dts: at91: Configure I2C SCL
gpio as open drain").
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Fixes: 19e5cef0 ("dt-bindings: i2c: at91: document optional bus recovery properties")

Documentation/devicetree/bindings/i2c/i2c-at91.txt

@@ -73,7 +73,7 @@ i2c0: i2c@f8034600 {
 	pinctrl-0 = <&pinctrl_i2c0>;
 	pinctrl-1 = <&pinctrl_i2c0_gpio>;
 	sda-gpios = <&pioA 30 GPIO_ACTIVE_HIGH>;
-	scl-gpios = <&pioA 31 GPIO_ACTIVE_HIGH>;
+	scl-gpios = <&pioA 31 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
 
 	wm8731: wm8731@1a {
 		compatible = "wm8731";