The 2.5 floppy driver has for a long time has two init/exit bugs:
1. It calls register_sys_device() on init, but fails to call
   unregister_sys_device() in exit. This leads to data structure
   corruption if floppy is a module and it gets unloaded.
2. If calls register_sys_device() early on init, but fails to call
   unregister_sys_device() if init fails. Again, this leads to
   data structure corruption.

The patch below fixes both these problems.