abx500-chargalg: Add abx500 charging algorithm

This is a charging algorithm driver for abx500 variants. It is the central
entity for battery driver and is responsible for charging and monitoring
the battery driver. It is a hardware independant driver and also monitors
other abx500 power supply devices.

Signed-off-by: Arun Murthy <arun.murthy@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>