extcon: arizona: Add device binding for the general purpose switch

The switch is generally used in conjunction with the MICDET clamp to
suppress pops and clicks associated with jack insertion. This patch adds
a binding that allows the user to select the mode of operation for this
switch.

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