iwlwifi: mvm: move the check if associated outside of the iterator for wowlan

Instead of checking if we are associated when suspending with wowlan
enabled in the interface iterator, allow it to return an unassociated
vif and move the check to the main suspend function.  This will be
needed by netdetect, since it should also work when we are not
associated but the vif is active.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>