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>