This module supports two loading parameters: default_margin, nodeamon. Their means are as followed:
	(1) default_margin: the timmer margin(in second) for watchdog to release an interrupt signal. Its default value is 60. It should not less than 0, and it will be set to 60 when it is 0.
	(2) nodeamon:  this value decides whether to create a kernel thread to feed the watchdog automatically. A kernel thread to feed the watchdog is created when it is 0, or there is no thread to be created. Its default value is 0. when the value is not 0, user program should feed the watchdog, or a reset signal will be sended to the system after 2 timer interrupt.
