ath9k: Fix ETSI compliance for AR9462 2.0

The minimum CCA power threshold values have to be adjusted
for existing cards to be in compliance with new regulations.
Newer cards will make use of the values obtained from EEPROM,
support for this was added earlier. To make sure that cards
that are already in use and don't have proper values in EEPROM,
do not violate regulations, use the initvals instead.

Cc: stable@vger.kernel.org
Reported-by: Jeang Daniel <dyjeong@qca.qualcomm.com>
Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>