Enable VXLAN on Spectrum-2 as previous patches added the required
functionality.

Note that for now Spectrum-1 and Spectrum-2 use the same function to
determine whether the VXLAN configuration is valid or not. In the
future, when the driver will be extended to support features not present
in Spectrum-1, two different functions will be needed.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>