ARM: dts: exynos: enable PMIC wakeup from suspend on Odroid X/U3

The RTC on Maxim max77686 PMIC can wakeup the system from suspend to
RAM.  Add a generic property for this.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210420164943.11152-6-krzysztof.kozlowski@canonical.com

arch/arm/boot/dts/exynos4412-odroid-common.dtsi

@@ -282,6 +282,7 @@ max77686: pmic@9 {
 		interrupts = <2 IRQ_TYPE_LEVEL_LOW>;
 		pinctrl-names = "default";
 		pinctrl-0 = <&max77686_irq>;
+		wakeup-source;
 		reg = <0x09>;
 		#clock-cells = <1>;