net/mlx5: add flow sync API

net/mlx5: add flow sync API

When creating a flow, the rule itself might not take effort
immediately once the function call returns with success. It would
take some time to let the steering synchronize with the hardware.

If the application wants the packet to be sent to hit the flow after
it is created, this flow sync API can be used to clear the steering
HW cache to enforce next packet hits the latest rules.

For TX, usually the NIC TX domain and/or the FDB domain should be
synchronized depends in which domain the flow is created.

The application could also try to synchronize the NIC RX and/or the
FDB domain for the ingress packets.

Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Ori Kam <orika@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>