net/mlx5e: Skip redundant checks when providing NUD lastuse feedback

It's redundant to continue the loop if we found one flow whose lastuse value
being newer than the last one we reported, since this is enough for us to
trigger a NUD update (neigh_event_send()).

Signed-off-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>