power: bq28400: Add support for bq28400 battery gauge

Add support for TI bq28400 SBS compliant battery gauge
The device communicates over I2C
The device supports reporting the battery status.
i.e. Current, Voltage, Temperature, Capacity etc.

Change-Id: Ieea8a47d0e8d4664c9a5c00e75792fe7f65676a5
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>