ARM: dts: exynos: enable PMIC wakeup from suspend on Midas

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

arch/arm/boot/dts/exynos4412-midas.dtsi

···
 		interrupts = <7 IRQ_TYPE_LEVEL_LOW>;
 		pinctrl-0 = <&max77686_irq>;
 		pinctrl-names = "default";
+		wakeup-source;
 		reg = <0x09>;
 		#clock-cells = <1>;