extcon: usb-gpio: use flags argument of devm_gpiod_get to set direction

Since 39b2bbe3

 (gpio: add flags argument to gpiod_get*() functions)
which appeared in v3.17-rc1, the gpiod_get* functions take an additional
parameter that allows to specify direction and initial value for output.

Without this patch there is no call to gpiod_direction_input but the
gpio is used for irq reporting and for that the line should be in input
mode.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>