mac80211: complete the mesh (interface handling) code

This completes the mesh interface handling code and a few other
bits about the mac80211 module.

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