arm64: dts: imx8mq-librem5: make the volume buttons a wakeup source

They turn on the display currently so to be consistent, let's make
them wake the system from suspend as well.

arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi

@@ -54,6 +54,7 @@
 			gpios = <&gpio1 17 GPIO_ACTIVE_LOW>;
 			linux,code = <KEY_VOLUMEDOWN>;
 			debounce-interval = <50>;
+			wakeup-source;
 		};
 
 		vol-up {
@@ -61,6 +62,7 @@
 			gpios = <&gpio1 16 GPIO_ACTIVE_LOW>;
 			linux,code = <KEY_VOLUMEUP>;
 			debounce-interval = <50>;
+			wakeup-source;
 		};
 	};