extcon: arizona: Factor out microphone and button detection

Continue refactoring the microphone detect handling by factoring
out the handling for microphone detection and button detection
into separate functions. This both makes the code a little clearer
and prepares for some planned future refactoring to make the state
handling in the driver more explicit.

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