in the Public Safety Band):
o add channel flags to identify half/quarter-rate operation
o add rate sets (need to check spec on 4Mb/s in 1/4 rate)
o add if_media definitions for new rates
o split net80211 channel setup out into ieee80211_chan_init
o fixup ieee80211_mhz2ieee and ieee80211_ieee2mhz to understand half/quarter
rate channels: note we temporarily use a nonstandard/hack numbering that
avoids overlap with 2.4G channels because we don't (yet) have enough
state to identify and/or map overlapping channel sets
o fixup ieee80211_ifmedia_init so it can be called post attach and will
recalculate the channel list and associated state; this enables changing
channel-related state like the regulatory domain after attach (will be
needed for 802.11d support too)
o add ieee80211_get_suprates to return a reference to the supported rate
set for a given channel
o add 3, 4.5, and 27 MB/s tx rates to rate <-> media conversion routines
o const-poison channel arg to ieee80211_chan2mode
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