extcon: max77693: Fix bug of wrong pointer when platform data is not used

This patch fix wrong pointer of platform data. If each machine set
platform data for h/w path or delay time of workqueue, this driver
happen kernel panic related to null pointer.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>