net/mlx5: DR, Allow insertion of duplicate rules

Duplicate rules were not allowed to be configured with SW steering.
This restriction caused failures with the replace rule logic done by
upper layers.

This fix allows for multiple rules with the same match values, in
such case the first inserted rules will match.

Fixes: 41d07074

 ("net/mlx5: DR, Expose steering rule functionality")
Signed-off-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>