selftests: mlxsw: egress_vid_classification: Fix the diagram

The topology diagram implies that $swp1 and $swp2 are members of the bridge
br0, when in fact only their uppers, $swp1.10 and $swp2.10 are. Adjust the
diagram.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>