AA: rt2800usb: merge a fix to slow down tx status polling (#13523)

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

Backport of r38452

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@38455 3c298f89-4303-0410-b956-a3cf2f4a3e73