ath9k: add some calibration fixes from wireless-testing

Backport r35081

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@35082 3c298f89-4303-0410-b956-a3cf2f4a3e73
uClibc: backport useful fixes from trunk (#12777)

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@35088 3c298f89-4303-0410-b956-a3cf2f4a3e73
ath9k: add updated tx gain tables, fixes stability issues on TL-WDR4300 and other devices

Backport of r35089

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@35090 3c298f89-4303-0410-b956-a3cf2f4a3e73