scsi: target: Use config_item_name() instead of open-coding it

Some target code uses config_item_name() while other code accesses .ci_name
directly. Make the target code consistent by switching to
config_item_name().

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>