power: pmic: add the max8997 controller for DM

Add the max8997 controller for Driver model.
Exynos4210 is using max8997 pmic controller.
(pmic_max8997.c should be deprecated.)

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>