selftests: forwarding: bridge_mdb_max: Add a new selftest

Add a suite covering mcast_n_groups and mcast_max_groups bridge features.
Signed-off-by: NPetr Machata <petrm@nvidia.com>
Acked-by: NNikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tools/testing/selftests/net/forwarding/Makefile

@@ -4,6 +4,7 @@ TEST_PROGS = bridge_igmp.sh \
 	bridge_locked_port.sh \
 	bridge_mdb.sh \
 	bridge_mdb_host.sh \
+	bridge_mdb_max.sh \
 	bridge_mdb_port_down.sh \
 	bridge_mld.sh \
 	bridge_port_isolation.sh \