[MAC80211]: remove fake set_key() call

Remove adding a fake key with a NONE key algorithm for each
associated STA. If we have hardware with such TX filtering
we should probably extend the sta_table_notification()
callback with the sta information instead; the fact that
it's treated as a key for some atheros hardware shouldn't
bother the stack.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>