wl12xx: handle idle changes per-interface

Idle changes are currently handled per hardware.
However, some operations should be done only per-interface.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>