pmic:fuel-gauge: Support for MAX17042 fuel-gauge

Support for MAX17042 fuel-gauge (FG), which is built into the MAX8997
power management device.
Special file - fg_battery_cell_params.h with cells characteristics
added.

The FG device will work with redesigned PMIC framework.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Stefano Babic <sbabic@denx.de>