ath9k_hw: fix endian issues with CTLs on AR9003

Parsing data using bitfields is messy, because it makes endian handling
much harder. AR9002 and earlier got it right, AR9003 got it wrong.
This might lead to either using too high or too low tx power values,
depending on frequency and eeprom settings.
Fix it by getting rid of the CTL related bitfields entirely and use
masks instead.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>