ab8500-btemp: AB8500 battery temperature driver

This driver is responsible for battery detection, obtaining battery
temperature and monitor the battery temperature by taking precautionary
measurements when battery temperature goes beyond or below the thresholds.

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>