I am a college graduate, but I can tell you from my experience that the only degree one would ever need to become a novelist is the one that life itself hands you.
Not unlike the manner in which an oyster is so irritated by the presence of a grain of sand that it secretes such a buildup of lubricants that then become a magnificent pearl, more often than not, the challenges and pain you encounter in life can be fodder for some wonderful writing.
If I'm not mistaken, none of the following famous authors had college degrees (well, maybe they received honorary degrees because of their literary contributions, but you know what I mean):
William Shakespeare, Jane Austen, Mark Twain, Ernest Hemingway, Charles Dickens, Dylan Thomas, Agatha Christie, and--yes--even J. K. Rowling!
Great question, cianeko! I learned some new things as a result of researching an answer for you. Thanks for sharing!