MFC r337570-r337573

r337570:
bwi(4): Set ic->ic_softc before bwi_getradiocaps to avoid bad deref

r337571:
net80211: Drain ageq before cleaning it up.

The comment above ieee80211_ageq_cleanup specifically notes that the queue
is assumed to be empty, and in order to make it so, ieee80211_ageq_drain
must be used.

r337572:
ieee8021_node: fix whitespace issues

r337573:
ath: Minor style cleanups

device_printf => DPRINTF and two whitespace adjustments