scsi: target: target_core_transport.c: enable+fix kernel-doc

For exported functions that already have near-kernel-doc notation,
fix them to begin with "/**" and make a few corrections so that they
don't have any kernel-doc warnings.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
To: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Cc: linux-scsi@vger.kernel.org
Cc: target-devel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>