ath5k: Port to new bitrate/channel API

Author: Nick Kossifidis <mickflemm@gmail.com>

Tested on 5211, 5213+5112, 5213A+2112A and it wors fine.

Also i figured out a way to process rate vallue found
on status descriptors, it's still buggy but we are getting
closer (i think it improved stability a little).

Changes to hw.c, initvals.c, phy.c
Changes-licensed-under: ISC

Changes to ath5k.h, base.c, base.h
Changes-licensed-under: 3-Clause-BSD

Acked-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@winlab.rutgers.edu>
Signed-off-by: John W. Linville <linville@tuxdriver.com>