net/mlx5e: MACsec, block offload requests with encrypt off

Currently offloading MACsec with authentication only (encrypt
property set to off) is not supported, block such requests
when adding/updating a macsec device.

Fixes: 8ff0ac5 ("net/mlx5: Add MACsec offload Tx command support")
Signed-off-by: Emeel Hakim <ehakim@nvidia.com>
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c

@@ -458,6 +458,11 @@ static bool mlx5e_macsec_secy_features_validate(struct macsec_context *ctx)
 		return false;
 	}
 
+	if (!ctx->secy->tx_sc.encrypt) {
+		netdev_err(netdev, "MACsec offload: encrypt off isn't supported\n");
+		return false;
+	}
+
 	return true;
 }