mac80211: use nl80211 interface types

There's really no reason for mac80211 to be using its
own interface type defines. Use the nl80211 types and
simplify the configuration code a bit: there's no need
to translate them any more now.

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