extcon: gpio: Add power resume support

When system on the suspend state, Some SoC can't get gpio interrupt.
After system resume, need send extcon uevent to userspace.

Signed-off-by: Rongjun Ying <rongjun.ying@csr.com>
Reviewed-by: Barry Song <Baohua.Song@csr.com>
Acked-by: Myungjoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>