extcon: usb-gpio: register extcon device before IRQ registration

IRQ handler touches info->edev, so if interrupt occurs before extcon
device initialization it can cause NULL pointer dereference. Doing extcon
initialization before IRQ handler registration fixes this problem.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>