b43/legacy: port to cfg80211 rfkill

This ports the b43/legacy rfkill code to the new API offered
by cfg80211 and thus removes a lot of useless stuff.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>