i40e: enable PTP

New feature: Enable PTP support in the i40e driver.

Change-ID: I6a8e799f582705191f9583afb1b9231a8db96cc8
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Matthew Vick <matthew.vick@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>