power_supply: Add new Nokia RX-51 (N900) power supply battery driver

This driver exporting battery design capacity, temperature and voltage for
battery in Nokia RX-51. This driver is needed for open source battery
management on Nokia RX-51 (N900).

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>