cleanup the rates structures used by ath5k. instead of separate driver and
mac80211 rate structures we now setup a static ieee80211_rate array and use it
directly. no conversion between two different rate structures has to be done
any more. a lot of unused and confusing junk was deleted.

renamed ath5k_getchannels into ath5k_setup_bands because this is what it does.
rewrote it to copy the bitrates correctly for each band. this is necessary for
running different hardware with the same driver (e.g. 5211 and 5212 based
cards).

add special handling of rates for AR5211 chipsets: it uses different rate codes
for CCK rates (which are actually like the other chips but with a 0xF mask).

setup a hardware code to rate index reverse mapping table for getting the rate
index of received frames.

the rates for control frames which have to be set in
ath5k_hw_write_rate_duration are now in one single array.

drivers/net/wireless/ath5k/ath5k.h:     Changes-licensed-under: ISC
drivers/net/wireless/ath5k/base.c:      Changes-licensed-under: 3-Clause-BSD
drivers/net/wireless/ath5k/base.h:      Changes-licensed-under: 3-Clause-BSD
drivers/net/wireless/ath5k/hw.c:        Changes-licensed-under: ISC
Signed-off-by: NBruno Randolf <br1@einfach.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>