mac80211: Fix behavior of ieee80211_open and ieee80211_close

This patch fixes:
- Incorrect calls to ieee80211_hw_config when the radiotap flag is set.
- Failure to actually unset the radiotap flag when all monitors are down.
- Failure to call ieee80211_hw_config after successful interface start.

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