ath9k: fix ath9k_hw_nvram_check_version()

There is a type bug so it always returns success.

Fixes: 6fa658fd ('ath9k: Simplify and fix eeprom endianness swapping')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>