vlan/macvlan: propagate transmission state to upper layers

Both vlan and macvlan devices usually don't use a qdisc and immediately
queue packets to the underlying device. Propagate transmission state of
the underlying device to the upper layers so they can react on congestion
and/or inform the sending process.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>