It is good to be clear about your goal from the start. But you must remember that life is a whole of your experiences in parts. College life is one such stage where you explore new dimensions of your personality. It is that time of your life where you take decisions for your career choices. So pursue that course in your graduation which is to your liking. To appear for civil services exam you need to have a graduation degree from any stream. Therefore, Either B.A or B.Sc. would suffice.