* Amlogic Meson SAR (Successive Approximation Register) A/D converter

Required properties:
- compatible:	depending on the SoC this should be one of:
			- "amlogic,meson-gxbb-saradc" for GXBB
			- "amlogic,meson-gxl-saradc" for GXL
			- "amlogic,meson-gxm-saradc" for GXM
		along with the generic "amlogic,meson-saradc"
- reg:		the physical base address and length of the registers
- clocks:	phandle and clock identifier (see clock-names)
- clock-names:	mandatory clocks:
			- "clkin" for the reference clock (typically XTAL)
			- "core" for the SAR ADC core clock
		optional clocks:
			- "sana" for the analog clock
			- "adc_clk" for the ADC (sampling) clock
			- "adc_sel" for the ADC (sampling) clock mux
- vref-supply:	the regulator supply for the ADC reference voltage
- #io-channel-cells: must be 1, see ../iio-bindings.txt

Example:
	saradc: adc@8680 {
		compatible = "amlogic,meson-gxl-saradc", "amlogic,meson-saradc";
		#io-channel-cells = <1>;
		reg = <0x0 0x8680 0x0 0x34>;
		clocks = <&xtal>,
			 <&clkc CLKID_SAR_ADC>,
			 <&clkc CLKID_SANA>,
			 <&clkc CLKID_SAR_ADC_CLK>,
			 <&clkc CLKID_SAR_ADC_SEL>;
		clock-names = "clkin", "core", "sana", "adc_clk", "adc_sel";
	};