station exiting power save mode prepend them to the driver's
send q instead of appending them. This insures the packets
are not misordered wrt any packets already q'd for the station.
This corrects a problem noticed when using a VoIP phone talking
to an ath card in ap mode; the misordered packets caused noise.
Submitted by: "J.R. Oldroyd" <jr@opal.com>
MFC after: 2 weeks