amd-xgbe: Add PPS periodic output support

Add support for hardware PPS (Pulse Per Second) output to the
AMD XGBE driver. The implementation enables flexible periodic
output mode, exposing it via the PTP per_out interface.

The driver supports configuring PPS output using the standard
PTP subsystem, allowing precise periodic signal generation for
time synchronization applications.

The feature has been verified using the testptp tool and
oscilloscope.

Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
Link: https://patch.msgid.link/20250909113143.1364477-1-Raju.Rangoju@amd.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>