power_supply: Add MAX17042 Fuel Gauge Driver

The MAX17042 is a fuel gauge with an I2C interface for lithium-ion
betteries. Unlike its predecessor MAX17040, MAX17042 uses 16bit
registers. Besides, MAX17042 has much more features than MAX17040; e.g.,
a thermistor, current and current accumulation measurement, battery
internal resistance estimate, average values of measurement, and others.

This patch implements a driver for MAX17042.
In this initial release, we have implemented the most basic features of
a fuel gauge: measure the battery capacity and voltage.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>