mac80211: Remove local->scan_flags

This patch removes all references to local->scan_flags as these are not
used anymore since the removal of prism2 ioctls.

Signed-off-by: Helmut Schaa <hschaa@suse.de>
Signed-off-by: Jiri Benc <jbenc@suse.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>