hwmon: (ltc4151) Add devicetree binding for ltc4151

LTC4151 High Voltage I2C Current and Voltage Monitor

Required properties:

- compatible: Must be "lltc,ltc4151"

- reg: I2C address

Optional properties:

- shunt-resistor-micro-ohms

	Shunt resistor value in micro-Ohms

	Defaults to <1000> if unset.

Example:

ltc4151@6e {

	compatible = "lltc,ltc4151";

	reg = <0x6e>;

	shunt-resistor-micro-ohms = <1500>;

};