ethdev: introduce flow engine configuration

ethdev: introduce flow engine configuration

The flow rules creation/destruction at a large scale incurs a performance
penalty and may negatively impact the packet processing when used
as part of the datapath logic. This is mainly because software/hardware
resources are allocated and prepared during the flow rule creation.

In order to optimize the insertion rate, PMD may use some hints provided
by the application at the initialization phase. The rte_flow_configure()
function allows to pre-allocate all the needed resources beforehand.
These resources can be used at a later stage without costly allocations.
Every PMD may use only the subset of hints and ignore unused ones or
fail in case the requested configuration is not supported.

The rte_flow_info_get() is available to retrieve the information about
supported pre-configurable resources. Both these functions must be called
before any other usage of the flow API engine.

Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
Acked-by: Ori Kam <orika@nvidia.com>
Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>