With concurrency managed workqueues, use of dedicated workqueues
can be replaced by using system_wq.
Drop visornic_timeout_reset_workqueue by using system_wq.
Since there is only one work item per devdata and different
devdatas do not need to be ordered, increase of concurrency
level by switching to system_wq should not break anything.
cancel_work_sync() is used to ensure that work is not pending or
executing on any CPU.