ina2xx properties

Required properties:
- compatible: Must be one of the following:
	- "ti,ina219" for ina219
	- "ti,ina220" for ina220
	- "ti,ina226" for ina226
	- "ti,ina230" for ina230
	- "ti,ina231" for ina231
- reg: I2C address

Optional properties:

- shunt-resistor
	Shunt resistor value in micro-Ohm

Example:

ina220@44 {
	compatible = "ti,ina220";
	reg = <0x44>;
	shunt-resistor = <1000>;
};