rfkill: call rfkill_led_trigger_unregister() on error

Code inspection turned up that error cases in rfkill_register() do not
call rfkill_led_trigger_unregister() even though we have already
registered.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>