In PG operator 2.2.0, I do not see any reference doc for How to add/update pg_hba conf entries. 

Good to have small example here https://docs.percona.com/percona-operator-for-postgresql/2.0/options.html 

Working Example:  

$  kubectl apply -f cr.yaml

$ kubectl get perconapgcluster cluster1 -n pgo -o yaml

Applied by operator:

{"pg_hba":["host all all 0.0.0.0/0 md5"]}

Also in patroni conf:

Applied to pg instance as well, 

New entry is added to pg instance pg_hba.conf