selftests/net: timestamping: add ptp v2 support

selftests/net: timestamping: add ptp v2 support

The timestamping tool is supporting now only PTPv1 (IEEE-1588 2002) while
modern HW often supports also/only PTPv2.

Hence timestamping tool is still useful for sanity testing of PTP drivers
HW timestamping capabilities it's reasonable to upstate it to support
PTPv2. This patch adds corresponding support which can be enabled by using
new parameter "PTPV2".

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://lore.kernel.org/r/20201029190931.30883-1-grygorii.strashko@ti.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>