count handling of station entries in hostap mode:
Input path:
o driver is now expected to find the node associated with the
sender of a received frame; use ic_bss if none is located
o driver passes the (referenced) node into ieee80211_input for
use within the wlan module and is responsible for cleaning up
on return
o the antenna state is no longer passed up with each frame; this
is now considered driver-private state and drivers are responsible
for keeping it in the driver-private part of a node
Output path:
Revamp output path for management frames to eliminate redundant
locking that causes problems and to correct reference counting
bogosity that occurs when stations are timed out due to inactivity
(in AP mode). On output the refcnt'd node is stashed in the pkthdr's
recvif field (yech) and retrieved by the driver. This eliminates
an unref/ref scenario and related node table unlock/lock due to the
driver looking up the node. This is particularly important when
stations are timed out as this causes a lock order reversal that
can result in a deadlock. As a byproduct we also reduce the overhead
for sending management frames (minimal). Additional fallout from
this is a change to ieee80211_encap to return a refcn't node for
tieing to the outbound frame. Node refcnts are not reclaimed until
after a frame is completely processed (e.g. in the tx interrupt
handler). This is especially important for timed out stations as
this deref will be the final one causing the node entry to be
reclaimed.
Additional semi-related changes:
o replace m_copym use with m_copypacket (optimization)
o add assert to verify ic_bss is never free'd during normal operation
o add comments explaining calling conventions by drivers for frames
going in each direction
o remove extraneous code that "cannot be executed" (e.g. because
pointers may never be null)
quietly discard them; this just permits them to be collected with bpf)
o add a counter for the number of rate control frames discarded when not in
monitor mode
o move the rx "too short" statistic in the stat structure so non-error rx stats
are together (NB: ABI change to apps that collect stats via driver ioctl)
mistakes (this mistake was not an issue because the length is only used to
decide whether or not to allocate a cluster)
o while here, move a beacon length comment to the "right place"
