mac80211: fixing null qos data frames check for reordering buffer

This patch fixes a wrong condition for null qos data frames, causing us to
drop data frames needed for reordering as well.

Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>