Heat the oil in a skillet over high heat; cook the mustard seeds in the hot oil until the seeds no longer are crackling. Stir the asafoetida powder into the mustard seeds; add the turnips, turnip leaves, and onion to the skillet. Season the mixture with the paprika, turmeric, and salt. Pour the water over the mixture, place a cover on the skillet, reduce heat to medium, and cook until the turnip is cooked yet remains crunchy, 5 to 7 minutes. Return heat to high to cook off any excess water. Mix the coconut into the mixture just before serving.