ath9k: Alternative EEPROM size for AR9003

AR9003 factory calibration allows to use bigger EEPROM than
standard 1k without changing the default layout. Allow
probing of EEPROM at alternative address if initial check
for default fails.
The original ar9003 eeprom ops are still be used.

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@neratec.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>