* Palmas general purpose ADC IP block devicetree bindings

Channels list:
	0 battery type
	1 battery temp NTC (optional current source)
	2 GP
	3 temp (with ext. diode, optional current source)
	4 GP
	5 GP
	6 VBAT_SENSE
	7 VCC_SENSE
	8 Backup Battery voltage
	9 external charger (VCHG)
	10 VBUS
	11 DC-DC current probe (how does this work?)
	12 internal die temp
	13 internal die temp
	14 USB ID pin voltage
	15 test network

Required properties:
- compatible : Must be "ti,palmas-gpadc".
- #io-channel-cells: Should be set to <1>.

Optional sub-nodes:
ti,channel0-current-microamp: Channel 0 current in uA.
	Values are rounded to derive 0uA, 5uA, 15uA, 20uA.
ti,channel3-current-microamp: Channel 3 current in uA.
	Values are rounded to derive 0uA, 10uA, 400uA, 800uA.
ti,enable-extended-delay: Enable extended delay.

Example:

pmic {
	compatible = "ti,twl6035-pmic", "ti,palmas-pmic";
	...
	gpadc {
		compatible = "ti,palmas-gpadc";
		interrupts = <18 0
			      16 0
			      17 0>;
		#io-channel-cells = <1>;
		ti,channel0-current-microamp = <5>;
		ti,channel3-current-microamp = <10>;
		};
	};
	...
};