BZ1991850: Adding ptp4lConf parameter to PtpConfig.yaml

[amolnar-rh]

Version(s): 4.8

Issue: https://bugzilla.redhat.com/show_bug.cgi?id=1991850

Link to docs preview: http://file.emea.redhat.com/amolnar/BZ1991850/networking/configuring-ptp.html#configuring-linuxptp_configuring-ptp

Additional information: This parameter is present in main and 4.9+.

[aireilly]

@aneeshkp Can you review this please

[djuran]

LGTM

[obochan-rh]

LGTM