bridge: vlan: Use correct flag name in comment

The flag used to indicate if a VLAN should be used for filtering - as
opposed to context only - on the bridge itself (e.g. br0) is called
'brentry' and not 'brvlan'.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>