wlcore: re-enable idle handling

We need some stuff done on idle change, most notably we have to stop
sched-scanning. Take care of this by reintroducing idle handling.

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