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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

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

···
 		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>;