This patch adds MFD driver for MAX77693 to enable its sub devices.

The MAX77693 is a multi-function devices. It includes PMIC,
MUIC(Micro USB Interface Controller), flash LED control and
haptic motor control.
Signed-off-by: NChanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: NMyungjoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>