scsi: target: Fix htmldocs warning in target_submit_prep()

Fix warning:

drivers/target/target_core_transport.c:1661: WARNING: Block quote ends
without a blank line; unexpected unindent.

Link: https://lore.kernel.org/r/20210318225858.11863-1-michael.christie@oracle.com
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_transport.c

@@ -1659,6 +1659,7 @@ EXPORT_SYMBOL_GPL(target_init_cmd);
  * Returns:
  *	- less than zero to signal failure.
  *	- zero on success.
+ *
  * If failure is returned, lio will the callers queue_status to complete
  * the cmd.
  */