kernel/bwn: Replace callout_drain calls. Replace a tsleep by DELAY.

* Adjusting local #include statements to conform to style(9).

* callout_drain calls are replaced by callout_stop_sync.

* Reverting a DELAY -> tsleep replacement.
devd.conf: Comment some entries where we lack support in one way or the other.

We'll gradually uncomment them again once they are known to work.