The following two patches add support for error propagation
through ->ndo_hard_start_xmit() and use it to propagate qdisc
submission state through VLAN and macvlan devices.

I'm also experimenting with returning errno codes from
tunnel devices to the originating socket, but those patches
still need some work.

The only change relative to the patch posted yesterday is
removal of an unnecessary initialization in dev_hard_start_xmit().