mlxsw: spectrum: PTP: Configure PTP traps and FIFO events

Configure MTPTPT to set which message types should arrive under which
PTP trap, and MOGCR to clear the timestamp queue after its contents are
reported through PTP_ING_FIFO or PTP_EGR_FIFO.

With this configuration, PTP packets start arriving through the PTP
traps. However since timestamping is disabled by default and there is
currently no way to enable it, they will not be timestamped.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>