net/mlx5: Fix multiple updates of steering rules in parallel

There might be a condition where the fte found is not active yet. In
this case we should not use it, but continue to search for another, or
allocate a new one.

Fixes: bd71b08e ("net/mlx5: Support multiple updates of steering rules in parallel")
Signed-off-by: Eli Britstein <elibr@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>