iwlwifi: mvm: capture connection loss as part of MLME trigger

The only other way to catch these would have been to monitor
the Tx deauth event, but we can send a deauth when we roam.
So it would have been tricky to make sure we capture the
connection losses only.
Define a separate trigger for the connection losses to make
it easier to catch them.

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