ARM: dts: zynq: replace gpio-key,wakeup with wakeup-source property

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 futher copy-paste
duplication.

Cc: Michal Simek <michal.simek@xilinx.com>
Cc: "Sören Brinkmann" <soren.brinkmann@xilinx.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/dts/zynq-zc702.dts

@@ -40,14 +40,14 @@
 			label = "sw14";
 			gpios = <&gpio0 12 0>;
 			linux,code = <108>; /* down */
-			gpio-key,wakeup;
+			wakeup-source;
 			autorepeat;
 		};
 		sw13 {
 			label = "sw13";
 			gpios = <&gpio0 14 0>;
 			linux,code = <103>; /* up */
-			gpio-key,wakeup;
+			wakeup-source;
 			autorepeat;
 		};
 	};