net: fix network drivers ndo_start_xmit() return values (part 4)

Fix up WAN drivers that return an errno value to qdisc_restart(), causing
qdisc_restart() to print a warning an requeue/retransmit the skb.

- cycx_x25: intention appears to be to requeue the skb

Does not compile cleanly for me even without this patch, so untested.

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