Rockchip Successive Approximation Register (SAR) A/D Converter bindings

Required properties:
- compatible: should be "rockchip,<name>-saradc" or "rockchip,rk3066-tsadc"
   - "rockchip,saradc": for rk3188, rk3288
   - "rockchip,rk3066-tsadc": for rk3036
   - "rockchip,rk3399-saradc": for rk3399

- reg: physical base address of the controller and length of memory mapped
       region.
- interrupts: The interrupt number to the cpu. The interrupt specifier format
              depends on the interrupt controller.
- clocks: Must contain an entry for each entry in clock-names.
- clock-names: Shall be "saradc" for the converter-clock, and "apb_pclk" for
               the peripheral clock.
- vref-supply: The regulator supply ADC reference voltage.
- #io-channel-cells: Should be 1, see ../iio-bindings.txt

Example:
	saradc: saradc@2006c000 {
		compatible = "rockchip,saradc";
		reg = <0x2006c000 0x100>;
		interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&cru SCLK_SARADC>, <&cru PCLK_SARADC>;
		clock-names = "saradc", "apb_pclk";
		#io-channel-cells = <1>;
		vref-supply = <&vcc18>;
	};