ath9k: add a fix for tx pending frame accounting, fixes some tx hang issues

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

Backport of r41673

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@41802 3c298f89-4303-0410-b956-a3cf2f4a3e73
mac80211: fix a null pointer deref when querying station info when rate control is not initialized (#17061)

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

Backport of r41801

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@41803 3c298f89-4303-0410-b956-a3cf2f4a3e73