mfd: arizona: Add register bits for general purpose switch

The switch is typically used in conjunction with the MICDET clamp in
order to suppress pops and clicks associated with jack insertion.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>