mac80211: remove useless DA checking in ieee80211_rx_mgmt_probe_resp()

Actually the DA field has already been checked along the rx path (in
prepare_for_handlers()) and this check is therefore useless at this point.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>