selftests: net: bridge: fix typo in vlan_filtering dependency test

Prior patch:
]# TESTS=vlmc_filtering_test ./bridge_vlan_mcast.sh
TEST: Vlan multicast snooping enable                                [ OK ]
Device "bridge" does not exist.
TEST: Disable multicast vlan snooping when vlan filtering is disabled   [FAIL]
        Vlan filtering is disabled but multicast vlan snooping is still enabled

After patch:
# TESTS=vlmc_filtering_test ./bridge_vlan_mcast.sh
TEST: Vlan multicast snooping enable                                [ OK ]
TEST: Disable multicast vlan snooping when vlan filtering is disabled   [ OK ]

Fixes: f5a9dd58 ("selftests: net: bridge: add test for vlan_filtering dependency")
Cc: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>