mac80211: remove port control enable switch, clean up sta flags

This patch removes the 802.1X port acess control enable flag
since it is not required. Instead, set the authorized flag for
each station that we normally communicate with (WDS peers, IBSS
peers and APs we're associated to) and require hostapd to set
the authorized flag for all stations when port control is not
enabled.

Also, since I was working in that area, this documents station
flags and removes the unused "permanent" one.

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