[NET]: rfkill: add support for input key to control wireless radio

The RF kill patch that provides infrastructure for implementing
switches controlling radio states on various network and other cards.

[dtor@insightbb.com: address review comments]
[akpm@linux-foundation.org: cleanups, build fixes]

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>