A product decision has been made to defeature detection of PTP frames
over L4 (UDP) on the XL710 MAC. Do not advertise support for L4
timestamping.

Change-ID: I41fbb0f84ebb27c43e23098c08156f2625c6ee06
Signed-off-by: NJacob Keller <jacob.e.keller@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>