mlxsw: reg: Add nve_flood_prf_id field to SFMR

The field is used for setting a flood profile for lookup of KVD entry for
NVE underlay. As the other uses of flood profile, this references a traffic
type-to-offset mapping, except here it is not applied to PGT offsets, but
KVD offsets.

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