mlxsw: reg: Add Tunneling NVE QoS Configuration Register

The register configures how QoS is set in Encapsulation into the
underlay network.

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