net/mlx5: Lag, don't use the hardcoded value of the first port

The cited commit didn't change the body of the loop as it should.
It shouldn't be using MLX5_LAG_P1.

Fixes: 7e978e7 ("net/mlx5: Lag, use actual number of lag ports")
Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Link: https://patch.msgid.link/20240730061638.1831002-5-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c

@@ -1538,7 +1538,7 @@ u8 mlx5_lag_get_slave_port(struct mlx5_core_dev *dev,
 		goto unlock;
 
 	for (i = 0; i < ldev->ports; i++) {
-		if (ldev->pf[MLX5_LAG_P1].netdev == slave) {
+		if (ldev->pf[i].netdev == slave) {
 			port = i;
 			break;
 		}