net/mlx5: DR, Fix matcher disconnect error flow

When 2nd flow rules arrives, it will merge together with the
1st one if matcher criteria is the same.

If merge fails, driver will rollback the merge contents, and
reject the 2nd rule. At rollback stage, matcher can't be
disconnected unconditionally, otherise the 1st rule can't be
hit anymore.

Add logic to check if the matcher should be disconnected or not.

Fixes: cc2295c ("net/mlx5: DR, Improve steering for empty or RX/TX-only matchers")
Signed-off-by: Rongwei Liu <rongweil@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Link: https://lore.kernel.org/r/20221026135153.154807-4-saeed@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/steering/dr_rule.c

@@ -1200,7 +1200,8 @@ dr_rule_create_rule_nic(struct mlx5dr_rule *rule,
 	}
 
 remove_from_nic_tbl:
-	mlx5dr_matcher_remove_from_tbl_nic(dmn, nic_matcher);
+	if (!nic_matcher->rules)
+		mlx5dr_matcher_remove_from_tbl_nic(dmn, nic_matcher);
 
 free_hw_ste:
 	mlx5dr_domain_nic_unlock(nic_dmn);