Before user space daemon start to access the watchdog device, there is a time interval that watchdog is disabled in the original flow. If the system freezing at this interval, it cannot be rebooted by watchdog hardware automatically. In order to solve this problem, the watchdog hardware should be kept working, and start hrtimer in framework to ping it by setting max_hw_heartbeat_ms and HW_RUNNING used in watchdog_need_worker to determine whether the worker should be started or not
