power: supply: Initial support for ROHM BD70528 PMIC charger block

ROHM BD70528 PMIC includes battery charger block. Support charger
staus queries and doing few basic settings like input current limit
and charging current.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>