Have you tried, and realized then that it wasn't possible? I'm guessing no...
At least, not that I have ever seen. I'm 99% sure you need to get a new card.
Well as I see it, you can do a few things. You can either delete some saves or buy another Memory Card. Also you could do what I did, buy Cheat software like a Codebreaker, which has limited Flash drive support, and transfer/ backup the saves to the flash drive, then delete the now backed-up saves on the Memory Card to free up space for the new games.