* Digi I/O Expander ADCs device tree bindings

The Digi I/O Expander ADC driver allows to read voltages from the MCA IOs that
are ADC capable. Check the I/O Expander ADC-capable IOs on the CC6UL Hardware
Reference Manual.

Required properties:
- compatible: must be "digi,mca-ioexp-adc".

Optional properties:
- adc-ch-list: list of I/O Expander IOs to be enabled as ADCs
- adc-vref: ADC reference voltage in uV.

Example:

	&mca_ioexp_adc {
		digi,adc-ch-list = <0 4>;
		digi,adc-vref = <3000000>;
	};
