ARM: dts: imx6qdl: tqma6: Mark gpio-buttons as wakeup-source

They are connected directly to CPU, so they can be used as wakeup source.
Signed-off-by: NAlexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl-mba6.dtsi

@@ -40,18 +40,21 @@
 			label = "s6";
 			linux,code = <KEY_F6>;
 			gpios = <&gpio7 13 GPIO_ACTIVE_LOW>;
+			wakeup-source;
 		};
 
 		button2 {
 			label = "s7";
 			linux,code = <KEY_F7>;
 			gpios = <&gpio7 12 GPIO_ACTIVE_LOW>;
+			wakeup-source;
 		};
 
 		button3 {
 			label = "s8";
 			linux,code = <KEY_F8>;
 			gpios = <&gpio1 8 GPIO_ACTIVE_LOW>;
+			wakeup-source;
 		};
 	};