mlxsw: reg: Add Policy-Engine eRP Table Register

The register is used to add and delete eRPs from the eRP table.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>