cfg80211: validate station settings

When I disallowed interfering with stations on non-AP interfaces,
I not only forget mesh but also managed interfaces which need
this for the authorized flag. Let's actually validate everything
properly.

This fixes an nl80211 regression introduced by the interfering,
under which wpa_supplicant -Dnl80211 could not properly connect.

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