ARM: dts: exynos: enable PMIC wakeup from suspend on Odroid XU

The RTC on Maxim max77802 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/20210420164943.11152-4-krzysztof.kozlowski@canonical.com

arch/arm/boot/dts/exynos5410-odroidxu.dts

@@ -190,6 +190,7 @@ max77802: pmic@9 {
 		pinctrl-names = "default";
 		pinctrl-0 = <&max77802_irq>, <&pmic_dvs_1>, <&pmic_dvs_2>,
 			    <&pmic_dvs_3>;
+		wakeup-source;
 		#clock-cells = <1>;
 
 		inl1-supply = <&buck5_reg>;