ethdev: negotiate delivery of packet metadata from HW to PMD

ethdev: negotiate delivery of packet metadata from HW to PMD

Provide an API to let the application control the NIC's ability
to deliver specific kinds of per-packet metadata to the PMD.

Checks for the NIC's ability to set these kinds of metadata
in the first place (support for the flow actions) belong in
flow API responsibility domain (flow validate mechanism).
This topic is out of scope of the new API in question.

The PMD's ability to deliver received metadata to the user
by virtue of mbuf fields should be covered by mbuf library.
It is also out of scope of the new API in question.

Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>
Acked-by: Ray Kinsella <mdr@ashroe.eu>
Acked-by: Jerin Jacob <jerinj@marvell.com>
Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Acked-by: Somnath Kotur <somnath.kotur@broadcom.com>
Acked-by: Ori Kam <orika@nvidia.com>
Acked-by: Wisam Jaddo <wisamm@nvidia.com>