dpif-netdev: Update offloaded flows statistics.

dpif-netdev: Update offloaded flows statistics.

In case a flow is HW offloaded, packets do not reach the SW, thus not
counted for statistics. Use netdev flow get API in order to update the
statistics of flows by the HW statistics.

Co-authored-by: Eli Britstein <elibr@mellanox.com>
Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Signed-off-by: Eli Britstein <elibr@mellanox.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>