RFKILL: set the status of the leds on activation.

Provide default activate function to set the state of the led
when the led becomes bound to the trigger

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: John W. Linville <linville@tuxdriver.com>