aoe: Fix OOPS after SKB queue changes.

Reported by Thomas Graf.

If we don't unlink the SKB from the queue when we send it
out in aoenet_xmit(), dev_hard_start_xmit() will see skb->next
as non-NULL and interpret this to mean the SKB is part of a
GSO segment list.

Add __skb_unlink() call to fix that.

Signed-off-by: David S. Miller <davem@davemloft.net>