Slave is now able to dequeue buffers from rx queue and enqueue them to tx queue
(zero-copy operation). Slave can produce buffers with headroom, which will allow adding
encap without copy.
Change-Id: Ia189f8de1a68be787545ed46cf78d36403e7e9bf
Signed-off-by: Jakub Grajciar <jgrajcia@cisco.com>
