scsi: remove left-over due to now gone pktcdvd shortcomings

Commit f40eb99 ("pktcdvd: remove driver.") removes the pktcdvd driver,
including the config CDROM_PKTCDVD and CDROM_PKTCDVD_WCACHE, and the uapi
header file.

Remove some further unneeded left-over due to now gone pktcdvd shortcomings
in the scsi library.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>

drivers/scsi/scsi_lib.c

@@ -2018,14 +2018,6 @@ struct scsi_device *scsi_device_from_queue(struct request_queue *q)
 
 	return sdev;
 }
-/*
- * pktcdvd should have been integrated into the SCSI layers, but for historical
- * reasons like the old IDE driver it isn't.  This export allows it to safely
- * probe if a given device is a SCSI one and only attach to that.
- */
-#ifdef CONFIG_CDROM_PKTCDVD_MODULE
-EXPORT_SYMBOL_GPL(scsi_device_from_queue);
-#endif
 
 /**
  * scsi_block_requests - Utility function used by low-level drivers to prevent