net: ethernet: ti: am65-cpts: fix timestamp loss due to race conditions

Resolve race conditions in timestamp events list handling between TX
and RX paths causing missed timestamps.

The current implementation uses a single events list for both TX and RX
timestamps. The am65_cpts_find_ts() function acquires the lock,
splices all events (TX as well as RX events) to a temporary list,
and releases the lock. This function performs matching of timestamps
for TX packets only. Before it acquires the lock again to put the
non-TX events back to the main events list, a concurrent RX
processing thread could acquire the lock (as observed in practice),
find an empty events list, and fail to attach timestamp to it,
even though a relevant event exists in the spliced list which is yet to
be restored to the main list.

Fix this by creating separate events lists to handle TX and RX
timestamps independently.

Fixes: c459f606 ("net: ethernet: ti: am65-cpts: Enable RX HW timestamp for PTP packets using CPTS FIFO")
Signed-off-by: Aksh Garg <a-garg7@ti.com>
Reviewed-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Link: https://patch.msgid.link/20251016115755.1123646-1-a-garg7@ti.com


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