mlxsw: spectrum_switchdev: Allow joining VxLAN to 802.1ad bridge

The previous patches added support for VxLAN device enslaved to 802.1ad
bridge in Spectrum-2 ASIC and vetoed it in Spectrum-1.

Do not veto VxLAN with 802.1ad bridge.

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>