net: dsa: b53: Let DSA handle mismatched VLAN filtering settings

The DSA core is now able to do this check prior to calling the
.port_vlan_filtering callback, so tell it that VLAN filtering is global
for this particular hardware.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Suggested-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>