Some drivers are ADDing the scsi command's result bytes instead of ORing
them.

While this can produce correct results it has unexpected side effects.
Signed-off-by: NJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>