cciss: fix bug if scsi tape support is disabled

Bug fix. If SCSI tape support is turned off we get an implicit declaration
of cciss_unregister_scsi error in cciss_remove_one.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: Stephen M. Cameron <scameron@beardog.cca.cpqcorp.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>