extcon: max77693: Use power efficient workqueue for delayed cable detection

Schedule delayed cable detection work on power efficient workqueue
so the scheduler won't wake up idle core for that work.
This extends the idle time for CPU cores and conserves power.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>