ethdev: add hairpin bind and unbind API

ethdev: add hairpin bind and unbind API

In single port hairpin mode, all the hairpin Tx and Rx queues belong
to the same device. After the queues are set up properly, there is
no other dependency between the Tx queue and its Rx peer queue. The
binding process that connected the Tx and Rx queues together from
hardware level will be done automatically during the device start
procedure. Everything required is configured and initialized already
for the binding process.

But in two ports hairpin mode, there will be some cross-dependences
between two different ports. Usually, the ports will be initialized
serially by the main thread but not in parallel. The earlier port
will not be able to enable the bind if the following peer port is
not yet configured with HW resources. What's more, if one port is
detached / attached dynamically, it would introduce more trouble
for the hairpin binding.

To overcome these, new APIs for binding and unbinding are added.
During startup, only the hairpin Tx and Rx peer queues will be set
up. Nothing will be done when starting the device if the queues are
without auto-bind attribute. Only after the required ports pair
started, the `rte_eth_hairpin_bind()` API can be called to bind the
all Tx queues of the egress port to the Rx queues of the peer port.
Then the connection between the egress and ingress ports pair will
be established.

The `rte_eth_hairpin_unbind()` API could be used to disconnect the
egress and the peer ingress ports. This should only be called before
the device is closed if needed. When doing the clean up, all the
egress and ingress pairs related to a single port should be taken
into consideration, especially in the hot unplug case.
mode is described.

Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Ori Kam <orika@nvidia.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>