gve: Add support to query the nic clock

gve: Add support to query the nic clock

Query the nic clock and store the results. The timestamp delivered
in descriptors has a wraparound time of ~4 seconds so 250ms is chosen
as the sync cadence to provide a balance between performance, and
drift potential when we do start associating host time and nic time.

Leverage PTP's aux_work to query the nic clock periodically.

Signed-off-by: Kevin Yang <yyd@google.com>
Signed-off-by: John Fraker <jfraker@google.com>
Signed-off-by: Tim Hostetler <thostet@google.com>
Signed-off-by: Ziwei Xiao <ziweixiao@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
Link: https://patch.msgid.link/20250614000754.164827-6-hramamurthy@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>