power: supply: max77650: Add support for battery charger

Add basic support for the battery charger for max77650 PMIC.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>