libnetlink: linkdump_req is done for AF_BRIDGE as well

libnetlink: linkdump_req is done for AF_BRIDGE as well

The bridge command 'vlan show' calls rtnl_linkdump_req_filter for
family AF_BRIDGE. Update rtnl_linkdump_req_filter to send the filter
for that family as well.

Fixes: d97b16b2c906 ("libnetlink: linkdump_req: Only AF_UNSPEC family expects an ext_filter_mask")
Reported-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Tested-by: Ido Schimmel <idosch@mellanox.com>