interrupt. If we want to use link state change interrupt ste(4)
should also implement auto-negotiation complete handler as well as
various PHY access handling. Now link state change is handled by
mii(4) polling so it will automatically update link state UP/DOWN
events which in turn make ste(4) usable with lagg(4).
r199559 added a private timer to drive watchdog and the timer also
used to drive MAC statistics update. Because the MAC statistics
update is called whenever statistics counter reaches near-full, it
drove watchdog timer too fast such that it caused false watchdog
timeouts under heavy TX traffic conditions.
Fix the regression by separating ste_stats_update() from driving
watchdog timer and introduce a new function ste_tick() that handles
periodic job such as driving watchdog, MAC statistics update and
link state check etc.
While I'm here clear armed watchdog timer in ste_stop().