scsi: st: Return error code in st_scsi_execute()

The callers to st_scsi_execute() already check for negative return values,
so we can drop the use of DRIVER_ERROR and return the actual error code.

Link: https://lore.kernel.org/r/20210427083046.31620-2-hare@suse.de


Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>