b43legacy: Fix rfkill radio LED

This fixes Bug #9414 for b43legacy. This patch is the equivalent of one
submitted earlier for b43.

Since addition of the rfkill callback, the LED associated with the off
switch on the radio has not worked for several reasons:

(1) Essential data in the rfkill structure were missing.
(2) The rfkill structure was initialized after the LED initialization.
(3) There was a minor memory leak if the radio LED structure was inited.

Once the above problems were fixed, additional difficulties were noted:

(4) The radio LED was in the wrong state at startup.
(5) The radio switch had to be manipulated twice for each state change.
(6) A circular mutex locking situation existed.
(7) If rfkill-input is built as a module, it is not automatically loaded.

This patch fixes all of the above and removes a couple of sparse warnings.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Stefano Brivio <stefano.brivio@polimi.it>
Signed-off-by: John W. Linville <linville@tuxdriver.com>