ARM: dts: exynos: enable PMIC wakeup from suspend on SMDK5420

The RTC on S2MPS11 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/exynos5420-smdk5420.dts

···
 	pmic@66 {
 		compatible = "samsung,s2mps11-pmic";
 		reg = <0x66>;
+		wakeup-source;
 
 		s2mps11_osc: clocks {
 			compatible = "samsung,s2mps11-clk";