iwlwifi: mvm: prevent sched scan while not idle

Prevent sched scan while not idle (including during association or in AP
mode) instead of while associated only.

This fixes my previous commit which was incomplete:

commit bd5e4744
Author: David Spinadel <david.spinadel@intel.com>
Date:   Thu Apr 24 13:15:29 2014 +0300

    iwlwifi: mvm: do no sched scan while associated

    Currently the FW doesn't support sched scan while associated,
    Prevent it.

Signed-off-by: David Spinadel <david.spinadel@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>