I had some discussion with Ben Collins on ow to properly allow
hotplugging of ieee1394 storage device (sbp2).  While the scsi_add_host/
scsi_remove_host interface allows hotpluging of ieee1394 adapters we
need a way to register the actual devices with the scsi layer when
they're plugged in.  I've restructured the code to handle the
/proc/scsi/scsi code to add/remove devices a bit to have an interface
the ieee1394 driver can use, and created the following new interface:

	struct scsi_device *scsi_add_device(struct Scsi_Host *shost,
			uint channel, uint id, uint lun)
	int scsi_remove_device(struct scsi_device *sdev)

in addition scsi_probe_and_add_lun() got some overhaul to become
readable and can now return the struct scsi_device it probed as an
optional argument.