ath5k: revert AHB bus support removing

ath5k: revert AHB bus support removing

This reverts commit 5cde72e09f5a68e2f7185f17e540dd5a4a6bd651.

AHB bus code has been removed, since we did not have support Atheros
AR231x SoC, required for building the AHB version of ath5k. Now that
support WiSoC chips added we can restore functionality back.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Acked-by: John W. Linville <linville@tuxdriver.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Nick Kossifidis <mickflemm@gmail.com>
Cc: "Luis R. Rodriguez" <mcgrof@do-not-panic.com>
Cc: linux-wireless@vger.kernel.org
Cc: ath5k-devel@lists.ath5k.org
Cc: Linux MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/8247/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>