scsi: libsas: Fix an error code in sas_ata_add_dev()

This code accidentally returns success instead of -ENOMEM.

Fixes: 7cc7646b ("scsi: libsas: Factor out sas_ata_add_dev()")
Link: https://lore.kernel.org/r/Y7asLxzVwQ56G+ya@kili


Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>