When checksum offload is disabled in the driver via ethtool,
the PTP 1-step sync packets contain incorrect checksum, since
the stack calculates the checksum before driver updates
PTP timestamp field in the packet. This results in PTP packets
getting dropped at the other end. This patch fixes the issue by
re-calculating the UDP checksum after updating PTP
timestamp field in the driver.

Fixes: 2958d17a ("octeontx2-pf: Add support for ptp 1-step mode on CN10K silicon")
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
Link: https://lore.kernel.org/r/20230222113600.1965116-1-saikrishnag@marvell.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>