scsi: core: Remove an incorrect comment

scsi: core: Remove an incorrect comment

scsi_device.sdev_target is used in more code than the single_lun code,
hence remove the comment next to the definition of the sdev_target member.

Link: https://lore.kernel.org/r/20210415220826.29438-3-bvanassche@acm.org
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>