Changes:

   - add SYNCHRONIZE_CACHE command support
   - clean up module removal noise
   - add some more parameters for driverfs

merges work from Patrick
Mansfield. There are now options to set:
   - max_luns (default 2)
   - scsi_level (default 3)

Now if multiple scsi_debug pseudo devices are selected
they will get these tuples (assuming "2" is the next
available host number):
   2 0 0 0
   2 0 0 1
   2 0 1 0
   2 0 1 1
   2 0 2 0
   ...
   2 0 7 1
   3 0 0 0
   3 0 0 1
etc