extcon: adc-jack: Fix incompatible pointer type warning

This patch fixes the incompatible warning of extcon-adc-jack.c driver
when calling devm_extcon_dev_allocate().

Signed-off-by: Peter Foley <pefoley2@pefoley.com>
[cw00.choi: Modify the patch title and descritpion]
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>