ath5k: struct ath5k_desc cleanups

ath5k: struct ath5k_desc cleanups

* make struct ath5k_desc clearer by directly including unions of structures,
  which correspond to the hardware descriptors of different HW versions (5210
  and 5212). before they were casted at onto ath5k_desc at different points
  (e.g.  ds_hw[2]).

* rename some structures and variable names to make their use clearer, e.g.
  struct ath5k_hw_4w_tx_desc to ath5k_hw_4w_tx_ctl.

* substitute "old" with "5210" and "new" with "5212" (eg. rename
  ath5k_hw_proc_new_rx_status() to ath5k_hw_proc_5212_rx_status()) because old
  and new are relative and we might have a newer structure at some point.

* unify structs ath5k_hw_old_rx_status and ath5k_hw_new_rx_status into one
  ath5k_hw_rx_status, because they only differ in the flags and masks.

drivers/net/wireless/ath5k/ath5k.h:     Changes-licensed-under: ISC
drivers/net/wireless/ath5k/debug.c:     Changes-licensed-under: GPL
drivers/net/wireless/ath5k/hw.c:        Changes-licensed-under: ISC
drivers/net/wireless/ath5k/hw.h:        Changes-licensed-under: ISC

Signed-off-by: Bruno Randolf <bruno@thinktube.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>