extcon: arizona: Fix race with microphone detection and removal

The microphone detection code is run as delayed work to provide
additional debounce, it is possible that the jack could have been
removed by the time we process the microphone detection. Turn this
case into a no op.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>