scsi: bsg: Drop needless assignment in scsi_bsg_sg_io_fn()

Commit ce70fd9a

 ("scsi: core: Remove the cmd field from struct
scsi_request") refactored scsi_bsg_sg_io_fn() 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 scsi_bsg_sg_io_fn().

No functional change. No change in resulting object code.

Link: https://lore.kernel.org/r/20220315055325.14974-1-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>