regulator: TI bq24022 Li-Ion Charger driver

This adds a regulator driver for the TI bq24022 Single-Chip
Li-Ion Charger with its nCE and ISET2 pins connected to GPIOs.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>