Heat the oil in a large skillet over medium heat. Add the onion and cook until tender, about 3 minutes. Stir in the garlic and chili powder and cook for 1 minute more. Stir in the beans and chicken broth and cook until the beans are warmed through, about 5 minutes. Mash the beans coarsely with the back of a wooden spoon, adding more chicken broth to moisten, if needed. Season with salt and pepper, to taste. Stir in the cilantro.