mac80211: reset TX info flags when frame will be reprocessed

The temporary TX info flags need to be cleared if the frame will
be processed through the TX handlers again, otherwise it can get
messed up. This fixes a bug that happened when an aggregation
session was stopped while the station was sleeping - some frames
might get transmitted marked as aggregation erroneously without
this fix.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>