Based on the work done with private Jira OCPBUGS-52171 it is needed to add a note in the documentation reporting that hardware timing is not available with primary interface when OVNKubernetes is used. So configurations like UDPv4 cannot work with the `br-ex` interface.

Following are the links to the documentation, where from my point of view makes sense to add the note.

OVN Migration doc link (only for releases from 4.16 and older):
- https://docs.redhat.com/en/documentation/openshift_container_platform/4.16/html/networking/ovn-kubernetes-network-plugin#migrate-from-openshift-sdn

PTP documentation link:
- https://docs.redhat.com/en/documentation/openshift_container_platform/4.16/html/networking/using-precision-time-protocol-hardware#about-ptp

all