mlxsw: Veto Q-in-VNI for Spectrum-1 ASIC

Implementation of Q-in-VNI is different between ASIC types, this set adds
support only for Spectrum-2.

Return an error when trying to create VxLAN device and enslave it to
802.1ad bridge in Spectrum-1.

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>