rfkill: relicense header file

This header file is copied into userspace tools that
need not be GPLv2 licensed, make that easier.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Acked-by: Iñaky Pérez-González <inaky@linux.intel.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Acked-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Acked-by: Michael Buesch <mb@bu3sch.de>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>