net: bridge: Allow bridge master in br_vlan_get_info()

Mirroring offload in mlxsw needs to check that a given VLAN is allowed
to ingress the bridge device. br_vlan_get_info() is the function that is
used for this, however currently it only supports bridge port devices.
Extend it to support bridge masters as well.

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