power: supply: bq27xxx: Add support for BQ27426

This device is software similar to the BQ27426 except it has
different data memory offsets. Add support here.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>