net/mlx5: Correctly initialize last use of flow counters

Currently, last use timestamp is initialized to zero.
This is not the expected value by higher layers such as
when we do TC action offloading. To fix that, set it to
the current time, e.g when the counter/rule is offloaded.
This is the same behaviour of non-offloaded TC actions.

Fixes: 43a335e0 ('mlx5_core: Flow counters infrastructure')
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>