scsi: scsi_ioctl: Drop needless assignment in sg_io()

Commit ce70fd9a

 ("scsi: core: Remove the cmd field from struct
scsi_request") refactored sg_io(), so that it does not allocate directly
and hence does not return -ENOMEM in its error case. That makes a remaining
assignment of -ENOMEM to the return variable needless.

Drop this needless assignment in sg_io().

No functional change. No change in resulting object code.

Link: https://lore.kernel.org/r/20220315061520.30745-1-lukas.bulwahn@gmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>