This patch fixes stale mac80211_tx_control_flags for
filtered / retried frames.

Because ieee80211_handle_filtered_frame feeds skbs back
into the tx path, they have to be stripped of some tx
flags so they won't confuse the stack, driver or device.

Cc: <stable@kernel.org>
Acked-by: NJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: NChristian Lamparter <chunkeey@googlemail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>