staging: dpaa2-switch: add .ndo_start_xmit() callback

Implement the .ndo_start_xmit() callback for the switch port interfaces.
For each of the switch ports, gather the corresponding queue
destination ID (QDID) necessary for Tx enqueueing.

We'll reserve 64 bytes for software annotations, where we keep a skb
backpointer used on the Tx confirmation side for releasing the allocated
memory. At the moment, we only support linear skbs.

Also, add support for the Tx confirmation path which for the most part
shares the code path with the normal Rx queue.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>