greybus: svc_watchdog: use schedule_delayed_work helper

Instead of using the queue_delayed_work call for delayed work on
system_wq, use the schedule_delayed_work helper to be more consistent on
the style.

Testing Done:
 - Check SVC watchdog is pining after the change.

Signed-off-by: David Lin <dtwlin@google.com>
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>