net: dsa: hellcreek: Replace bogus comment

Replace bogus comment about matching the latched timestamp to one of the
received frames. That comment is probably copied from mv88e6xxx and true for
these switches. However, the hellcreek switch is configured to insert the
timestamp directly into the PTP packets.

While here, remove the other comments regarding the list splicing and locking as
well, because it doesn't add any value.

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20230801131647.84697-1-kurt@linutronix.de


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