ath9k: Fix bug in EEPROM chainmask retrieval

Using wrong chainmasks would have an adverse impact on performance.
This patch fixes chainmask retrieval for non-PCIE cards.

Signed-off-by: Sujith <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>