ARM: dts: imx6q: replace gpio-key,wakeup with wakeup-source for Utilite Pro

Though the keyboard driver for GPIO buttons(gpio-keys) will continue to
check for/support the legacy "gpio-key,wakeup" boolean property to
enable gpio buttons as wakeup source, "wakeup-source" is the new
standard binding.

This patch replaces the legacy "gpio-key,wakeup" with the unified
"wakeup-source" property in order to avoid any further copy-paste
duplication.

Cc: Sascha Hauer <kernel@pengutronix.de>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6q-utilite-pro.dts

@@ -68,7 +68,7 @@ power {
 			label = "Power Button";
 			gpios = <&gpio1 29 GPIO_ACTIVE_LOW>;
 			linux,code = <KEY_POWER>;
-			gpio-key,wakeup;
+			wakeup-source;
 		};
 	};