iwlwifi: mvm: fix scan iteration complete notification handling

Scan iteration complete notification handling uses the wrong FW API
version (version 2 instead of version 3).
Fix that by removing version 2 API which is no longer used, and using
only the updated version.

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