mlxsw: spectrum_ptp: Add helper functions to configure PTP traps

MTPTPT register is used to set which message types should arrive under
which PTP trap. Currently, PTP0 is used for event message types, which
means that the packets require time stamp. PTP1 is used for other packets.

This configuration will be same for Spectrum-2 and newer ASICs. In
preparation for Spectrum-2 PTP support, add helper functions to
configure PTP traps and use them for Spectrum-1. These functions will be
used later also for Spectrum-2.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>