uas: Remove comment about registering a uas scsi controller for each usb bus

Although an interesting concept, I don't think that this is a good idea:

-This will result in lots of "virtual" scsi controllers confusing users
-If we get a scsi-bus-reset we will now need to do a usb-device-reset of all
 uas devices on the same usb bus, which is something to avoid if possible

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>