mlxsw: reg: Add Router Egress Interface to VID Register

The REIV maps {egress router interface (eRIF), egress_port} -> {vlan ID}.
As preparation for unified bridge model, add REIV register for future use.

In the past, firmware would take care of the above mentioned mapping,
but in the new model this should be done by software using REIV register.

REIV register supports a simultaneous update of 256 ports using
'port_page' field. When 'port_page'=0 the records represent ports
0-255, when 'port_page'=1 the records represent ports 256-511 and so
on.

The register is reserved while using the legacy model.

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>