extcon: arizona: Simplify micd_pol_gpio handling

Currently we handle both old style GPIO and new style GPIOD differently
simplify this slightly by converting the old style GPIO to a GPIOD and
just using that from then on.

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