ath9k: use common read/write ops on pci and debug code

PCI and debug code will not be shared between ath9k and
ath9k_htc, so make that code use the common read/write ops.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>