nl80211: relicense nl80211.h under the ISC

We have a few BSD/ISC licensed userspace applications which
include nl80211.h from the kernel. To avoid legal ambiguity
for usage of the header file in these projects we rather simply
relicense the header file under the ISC. We've received consent
from all contributors to it.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Acked-by: Luis Carlos Cobo <luisca@cozybit.com>
Acked-by: Michael Buesch <mb@bu3sch.de>
Acked-by: Jouni Malinen <jouni.malinen@atheros.com>
Acked-by: Colin McCabe <colin@cozybit.com>
Acked-by: Javier Cardona <javier@cozybit.com>
Cc: johannes@sipsolutions.net
Cc: altape@eden.rutgers.edu
Cc: luisca@cozybit.com
Cc: mb@bu3sch.de
Cc: jouni.malinen@atheros.com
Cc: colin@cozybit.com
Cc: javier@cozybit.com
Signed-off-by: John W. Linville <linville@tuxdriver.com>