scsi: sd: Fix kdoc comment format

Fix the kdoc comment of the function sd_ioctl_common() to avoid a compiler
warning when compiling with W=1.

No functional changes.

Link: https://lore.kernel.org/r/20200706123354.452047-1-damien.lemoal@wdc.com


Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>