scsi: zfcp: silence all W=1 build warnings for existing kdoc

While at it also improve some copy & paste kdoc mistakes.

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>