SOC PMIC Syscon Driver

The driver is developed for UNISOC platform's PMIC, which is used by PMIC's
multi modules for finding PMIC's address easier.

Required properties:
-compatible:
 -"sprd,sc27xx-syscon" for SC27XX series pmic syscon
 -"sprd,ump962x-syscon" for UMP962x main pmic syscon
 -"sprd,ump9621-syscon" for UMP9621 sub-pmic syscon
 -"sprd,ump9622-syscon" for UMP9622 sub-pmic syscon
- reg: Specifies the PMIC's physical global address.

Example:
syscon@1800 {
	compatible = "sprd,sc2731-syscon", "sprd,sc27xx-syscon";
	reg = <0x1800>, <0x1ba0>, <0x1b98>;
};
