rt2x00: Fix LED state handling

For every global LED state change (register/unregister,
suspend/resume) we should force the LEDS to turn off.
This makes sure that the LEDS will always be in a sane
state after the state switch.

Note that when unregister is called but the LED class
wasn't resumed yet, we shouldn't change the LED state
since we might not have access to the device (device
was unplugged while suspended).

Also remove the checks in the activity, assoc and
radio LEDS which blocked calls to brightness_set()
when the state hasn't changed. Some of those LEDS
could be enabled by themselves when something happens
in the hardware (e.g. firmware is loaded). We already
did called rt2x00leds to switch the LED off, but those
calls were blocked.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>