The following involves editing a game file so it is advised that you create a backup copy of the file before proceeding. Use the iPhone Browser or a similar app to enter the '/var/mobile/Driver/Driver.app/data' directory and edit the 'mladder.dml' file and find the following lines:
Delete ALL the lines above those entries, then start the game and begin a new undercover career. The ending sequences and credits will begin and the cheat options will be unlocked afterwards. To return your game to standard Career mode just copy your original 'mladder.dml' file to it's original location.