gpio-charger: Add gpio_charger_resume

Gpio charger should notify if the gpio state had changed
during suspend. This will send a CHANGED event each time
the system resumes, ensuring a plug/unplug of the charger
is not missed.

Signed-off-by: Benson Leung <bleung@chromium.org>
Acked-By: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>