scsi_debug version 1.68 mark III

lk 2.5.65 seems a long time coming so here is a third patch on the scsi_debug driver. My "mark II" version is in
http://linux-scsi.bkbits.net:8080/scsi-misc-2.5
so the attachment is against that version.

Changelog since version 1.68 mark II:
- merge Mike Anderson's probe() cleanup
- num_devs is now "per host"
- num_devs is sysfs writeable
- add slave_alloc skeleton code

So to simulate 154 disks (for example) one might use:

  # modprobe scsi_debug add_host=11 num_devs=14

With max_luns at its default value of 2, 14 is the maximum number of devices per host scsi_debug will respond to (i.e. 7 targets, each with 2 lus).

Documentation updated at:
http://www.torque.net/sg/sdebug25.html

Doug Gilbert