net/tap: allow RSS flow action

net/tap: allow RSS flow action

One of the main identified use cases for the tap PMD is to be used in
combination with the fail-safe PMD as a fallback for a physical device.

Fail-safe is very strict about making sure its current configuration is
properly applied to all slave devices, they get rejected otherwise in
order to maintain a consistent state.

The problem is that tap's RSS support is currently limited to the
default (non-Toeplitz) balancing performed by the kernel on all Rx
queues. While proper RSS support emulation in the tap PMD is a work in
progress, the lack of rte_flow counterpart prevents validation of the
above use case in the meantime.

Given that unlike most PMDs, tap is more about convenience than
performance, support for the RSS action can be temporarily faked with
a minimum amount of code and mostly correct behavior by treating it
like a QUEUE action. Traffic is directed to the first queue of the set.

Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Pascal Mazon <pascal.mazon@6wind.com>