mlxsw: spectrum_ptp: Add implementation for physical hardware clock operations

Implement physical hardware clock operations. The main difference between
the existing operations of Spectrum-1 and the new operations of Spectrum-2
is the usage of UTC hardware clock instead of FRC.

Add support for init() and fini() functions for PTP clock in Spectrum-2.

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
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>