mac80211: don't check sdata_running in vif notifier

The ip address of the vif can be set even before the
vif is up. requiring the vif to be up in the vif
notifier makes the notifer ignore this event, which
causes wrong arp filter configuration later on.

Reported-by: Eyal Shapira <eyal@wizery.com>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>