extcon: max77843: Add max77843 MUIC driver

This patch adds MAX77843 extcon driver to support for MUIC(Micro
USB Interface Controller) device by using EXTCON subsystem to handle
various external connectors.

Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>