ARM: ux500: fix proximity sensor button

The proximity sensor is connected to pin AH12 on newer HREFs,
that corresponds to pin offset 25 on gpio5, not gpio6.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/ste-hrefv60plus.dts

@@ -20,7 +20,7 @@ / {
 
 	gpio_keys {
 		button@1 {
-			gpios = <&gpio6 25 0x4>;
+			gpios = <&gpio5 25 0x4>;
 		};
 	};