scsi: sd: Fix function descriptions

Fix argument names and description of function documentation comments.
No functional change is introduced by this patch.

[mkp: verbify]

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>