mlxsw: pci_hw: Add 'time_stamp' and 'time_stamp_type' fields to CQEv2

The Completion Queue Element version 2 (CQEv2) includes various metadata
fields of packets.

Add 'time_stamp' and 'time_stamp_type' fields along with functions to
extract the seconds and nanoseconds for a future use.

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