ARM: dts: fix gpio-keys wakeup-source property

The keyboard driver for GPIO buttons(gpio-keys) checks for one of the
two boolean properties to enable gpio buttons as wakeup source:
1. "wakeup-source" or
2. the legacy "gpio-key,wakeup"

However juno, ste-snowball and emev2-kzm9d dts file have a undetected
"wakeup" property to indictate the wakeup source.

This patch fixes it by making use of "wakeup-source" property.

Cc: Magnus Damm <magnus.damm@gmail.com>
Acked-by: Simon Horman <horms@verge.net.au>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
diff --git a/arch/arm/boot/dts/emev2-kzm9d.dts b/arch/arm/boot/dts/emev2-kzm9d.dts
index 955c24e..8c24975 100644
--- a/arch/arm/boot/dts/emev2-kzm9d.dts
+++ b/arch/arm/boot/dts/emev2-kzm9d.dts
@@ -35,28 +35,28 @@
 
 		button@1 {
 			debounce_interval = <50>;
-			wakeup = <1>;
+			wakeup-source;
 			label = "DSW2-1";
 			linux,code = <KEY_1>;
 			gpios = <&gpio0 14 GPIO_ACTIVE_HIGH>;
 		};
 		button@2 {
 			debounce_interval = <50>;
-			wakeup = <1>;
+			wakeup-source;
 			label = "DSW2-2";
 			linux,code = <KEY_2>;
 			gpios = <&gpio0 15 GPIO_ACTIVE_HIGH>;
 		};
 		button@3 {
 			debounce_interval = <50>;
-			wakeup = <1>;
+			wakeup-source;
 			label = "DSW2-3";
 			linux,code = <KEY_3>;
 			gpios = <&gpio0 16 GPIO_ACTIVE_HIGH>;
 		};
 		button@4 {
 			debounce_interval = <50>;
-			wakeup = <1>;
+			wakeup-source;
 			label = "DSW2-4";
 			linux,code = <KEY_4>;
 			gpios = <&gpio0 17 GPIO_ACTIVE_HIGH>;