mac80211: consolidate calls to plink_frame_tx

Do all frame transfers in one place at the end of the
big switch statements.  sta->plid and sta->reason can
be passed in any case, since they are only used for
the frames that need them.  Remove assignments to locals
for values already stored in the sta structure.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>