[PATCH ver2] gdth: bugfix for the at-exit problems

gdth_exit would first remove all cards then stop the timer and would not sync with the timer function. This caused a crash in gdth_timer() when module was unloaded. So del_timer_sync the timer before we delete the cards. also a reboot notifier function was registered but is not needed anymore.

[PATCH ver2] gdth: bugfix for the at-exit problems

gdth_exit would first remove all cards then stop the timer and would not sync with the timer function. This caused a crash in gdth_timer() when module was unloaded. So del_timer_sync the timer before we delete the cards. also a reboot notifier function was registered but is not needed anymore.