net80211: add watchdog routines

[avos]

Summary

This implementation should replace driver-level watchdog implementations (and, as a result, reduce size of driver-specific code).

The watchdog can be enabled via
ic->ic_flags_ext |= IEEE80211_FEXT_WATCHDOG;
code line before calling ieee80211_ifattach();

[avos]

• Call ieee80211_tx_watchdog_refresh() before calling ic_transmit() / ic_raw_xmit(); that adds a possibility to call it from the callee error handler.
• Update watchdog timer only when transmission occurs.
• Add few more checks.

[avos]

Fix race between ieee80211_tx_watchdog_stop() and ieee80211_tx_watchdog_refresh().

[mizhka]

I would like to resurrect this patch as related to bug reports: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252725 & https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=250424

sys/net80211/ieee80211_freebsd.c

575–576

Hi,

I would like to ask few questions about this patch. As I see, tx_queued is incremented on transmission, but I don't see how it will be decremented in sunny day scenario. It's int16_t (max = 32768, then overflow)