UNISOC PMIC Keypad_led

The PMIC Keypad_led can work at LDO mode or current mode.

Required properties:
- compatible: Should be one of follow:
  "sprd,sc2731-keypad-led",
  "sprd,sc2723-keypad-led",
  "sprd,sc2721-keypad-led",
  "sprd,sc2730-keypad-led",
  "sprd,ump9620-keypad-led".

- reg: address of keypad led control register.

Examples:

led-controller@1b88 {
	compatible = "sprd,sc27xx-keypad-led", "sprd,sc2730-keypad-led";
	reg = <0x1b88>, <0x1b8c>;
};
