net: ti: icssg-prueth: Fix 1 PPS sync

The first PPS latch time needs to be calculated by the driver
(in rounded off seconds) and configured as the start time
offset for the cycle. After synchronizing two PTP clocks
running as master/slave, missing this would cause master
and slave to start immediately with some milliseconds
drift which causes the PPS signal to never synchronize with
the PTP master.

Fixes: 186734c1 ("net: ti: icssg-prueth: add packet timestamping and ptp support")
Signed-off-by: Meghana Malladi <m-malladi@ti.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: MD Danish Anwar <danishanwar@ti.com>
Link: https://patch.msgid.link/20241111095842.478833-1-m-malladi@ti.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>