ath9k_hw: Eeeprom changes for AR9485

Calibration data are stored at 4k address (0xfff). The cal data
for AR9485 is not compressed so its lengh can exceed 1024 limit,
take care of that.

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>