extcon: arizona: Update device tree binding for mic detect configurations

Update the device tree binding documentation to include documentation for
the wlf,micd-configs property that is used to specify the configurations
for headset polarity detection (CTIA / OTMP).

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