scsi: scsi_ioctl: Return error code when blk_rq_map_kern() fails

scsi: scsi_ioctl: Return error code when blk_rq_map_kern() fails

The callers of sg_scsi_ioctl() already check for negative return values, so
we can drop the usage of DRIVER_ERROR and return the error from
blk_rq_map_kern() instead.

Link: https://lore.kernel.org/r/20210427083046.31620-3-hare@suse.de
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>