ath9k: disable TX_IQ_ON_AGC_CAL on AR934x, should improve stability

git-svn-id: svn://svn.openwrt.org/openwrt@34979 3c298f89-4303-0410-b956-a3cf2f4a3e73
ath9k: disable TX_IQ_ON_AGC_CAL on AR934x, should improve stability

Backport of r34979

git-svn-id: svn://svn.openwrt.org/openwrt@34980 3c298f89-4303-0410-b956-a3cf2f4a3e73