ath5k: HW code cleanup

 * No code changes...

 * Split hw.c to multiple files for better maintenance and add some documentation on each file
   code is going to grow soon (eeprom.c for example is going to get much stuff currently developed
   on ath_info) so it's better this way.

 * Rename following functions to maintain naming scheme:

     ah_setup_xtx_desc -> ah_setup_mrr_tx_desc
     (Because xtx doesn't say much, it's actually
     a multi-rate-retry tx descriptor)

     ath5k_hw_put_tx/rx_buf - > ath5k_hw_set_tx/rxdp
     ath5k_hw_get_tx/rx_buf -> ath5k_hw_get_tx/rxdp
     (We don't put any "buf" we set descriptor pointers on hw)

     ath5k_hw_tx_start -> ath5k_hw_start_tx_dma
     ath5k_hw_start_rx -> ath5k_hw_start_rx_dma
     ath5k_hw_stop_pcu_recv -> ath5k_hw_stop_rx_pcu
     (It's easier this way to identify them, we also
     have ath5k_hw_start_rx_pcu which completes the
     set)

     ath5k_hw_set_intr -> ath5k_hw_set_imr
     (As in get_isr we set imr here, not "intr")

  * Move ath5k_hw_setup_rx_desc on ah->ah_setup_rx_desc so we can
    include support for different rx descriptors in the future

  * Further cleanups so that checkpatch doesn't complain
    (only some > 80 col warnings for eeprom.h and reg.h as usual
    due to comments)

  Tested on 5211 and 5213 cards and works ok.

Changes-licensed-under: ISC
Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>
Acked-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>