ath9k: uninline ath9k_io{read,write}32 routines

The spin_lock handling uses lots of instructions on some archs.
With this patch the size of the ath9k module will be significantly
smaller.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>