sensor: add MAX17262 fuel gauge driver and sample application

The MAX17262 is an ultra-low power fuel-gauge IC which implements the
Maxim ModelGauge m5 algorithm. The IC monitors a single-cell battery
pack and supports internal current sensing for up to 3.1A pulse
current. The IC provides best performance for batteries with 100mAhr
to 6Ahr capacity.

Signed-off-by: Matija Tudan <mtudan@mobilisis.hr>