iio: light: add DT bindings for Capella CM3605

Capella Microsystems CM3605

Ambient Light and Short Distance Proximity Sensor

The CM3605 is an entirely analog part which however require quite a bit of

software logic to interface a host operating system.

This ALS and proximity sensor was one of the very first deployed in mobile

handsets, notably it is used in the very first Nexus One Android phone from

2010.

Required properties:

- compatible: must be: "capella,cm3605"

- aset-gpios: GPIO line controlling the ASET line (drive low

  to activate the ALS, should be flagged GPIO_ACTIVE_LOW)

- interrupts: the IRQ line (such as a GPIO) that is connected to

  the POUT (proximity sensor out) line. The edge detection must

  be set to IRQ_TYPE_EDGE_BOTH so as to detect movements toward

  and away from the proximity sensor.

- io-channels: the ADC channel used for converting the voltage from

  AOUT to a digital representation.

- io-channel-names: must be "aout"

Optional properties:

- vdd-supply: regulator supplying VDD power to the component.

- capella,aset-resistance-ohms: the sensitivity calibration resistance,

  in Ohms. Valid values are: 50000, 100000, 300000 and 600000,

  as these are the resistance values that we are supplied with

  calibration curves for. If not supplied, 100 kOhm will be assumed

  but it is strongly recommended to supply this.

Example:

cm3605 {

	compatible = "capella,cm3605";

	vdd-supply = <&foo_reg>;

	aset-gpios = <&foo_gpio 1 GPIO_ACTIVE_LOW>;

	capella,aset-resistance-ohms = <100000>;

	interrupts = <1 IRQ_TYPE_EDGE_BOTH>;

	io-channels = <&adc 0x01>;

	io-channel-names = "aout";

};