net/mlx5: make enable_mpesw idempotent

The enable_mpesw() function returns -EINVAL if ldev->mode is not
MLX5_LAG_MODE_NONE. This means attempting to enable MPESW mode when it's
already enabled will fail. In contrast, disable_mpesw() properly checks
if the mode is MLX5_LAG_MODE_MPESW before proceeding, making it
naturally idempotent and safe to call multiple times.

Fix enable_mpesw() to return success if mpesw is already enabled.

Fixes: a32327a ("net/mlx5: Lag, Control MultiPort E-Switch single FDB mode")
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Shay Drori <shayd@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/1764602008-1334866-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: mosheshemesh2

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

@@ -67,12 +67,19 @@ static int mlx5_mpesw_metadata_set(struct mlx5_lag *ldev)
 
 static int enable_mpesw(struct mlx5_lag *ldev)
 {
-	int idx = mlx5_lag_get_dev_index_by_seq(ldev, MLX5_LAG_P1);
 	struct mlx5_core_dev *dev0;
 	int err;
+	int idx;
 	int i;
 
-	if (idx < 0 || ldev->mode != MLX5_LAG_MODE_NONE)
+	if (ldev->mode == MLX5_LAG_MODE_MPESW)
+		return 0;
+
+	if (ldev->mode != MLX5_LAG_MODE_NONE)
+		return -EINVAL;
+
+	idx = mlx5_lag_get_dev_index_by_seq(ldev, MLX5_LAG_P1);
+	if (idx < 0)
 		return -EINVAL;
 
 	dev0 = ldev->pf[idx].dev;