net: mscc: ocelot: move more PTP code from the lib to ocelot_ptp.c

Decongest ocelot.c a bit more by moving all PTP related logic (including
timestamp processing and PTP packet traps) to ocelot_ptp.c.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>