scsi: xen: Drop use of internal host codes

The error codes:

 - DID_TARGET_FAILURE

 - DID_NEXUS_FAILURE

 - DID_ALLOC_FAILURE

 - DID_MEDIUM_ERROR

are internal to the SCSI layer. Drivers must not use them because:

 1. They are not propagated upwards, so SG IO/passthrough users will not
    see an error and think a command was successful.

    xen-scsiback will never see this error and should not try to send it.

 2. There is no handling for them in scsi_decide_disposition() so if
    xen-scsifront were to return the error to the SCSI midlayer then it
    kicks off the error handler which is definitely not what we want.

Remove the use from xen-scsifront/back.

Link: https://lore.kernel.org/r/20220812010027.8251-2-michael.christie@oracle.comReviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/xen-scsifront.c

@@ -289,14 +289,6 @@ static unsigned int scsifront_host_byte(int32_t rslt)
 		return DID_TRANSPORT_DISRUPTED;
 	case XEN_VSCSIIF_RSLT_HOST_TRANSPORT_FAILFAST:
 		return DID_TRANSPORT_FAILFAST;
-	case XEN_VSCSIIF_RSLT_HOST_TARGET_FAILURE:
-		return DID_TARGET_FAILURE;
-	case XEN_VSCSIIF_RSLT_HOST_NEXUS_FAILURE:
-		return DID_NEXUS_FAILURE;
-	case XEN_VSCSIIF_RSLT_HOST_ALLOC_FAILURE:
-		return DID_ALLOC_FAILURE;
-	case XEN_VSCSIIF_RSLT_HOST_MEDIUM_ERROR:
-		return DID_MEDIUM_ERROR;
 	case XEN_VSCSIIF_RSLT_HOST_TRANSPORT_MARGINAL:
 		return DID_TRANSPORT_MARGINAL;
 	default:

drivers/xen/xen-scsiback.c

@@ -333,18 +333,6 @@ static int32_t scsiback_result(int32_t result)
 	case DID_TRANSPORT_FAILFAST:
 		host_status = XEN_VSCSIIF_RSLT_HOST_TRANSPORT_FAILFAST;
 		break;
-	case DID_TARGET_FAILURE:
-		host_status = XEN_VSCSIIF_RSLT_HOST_TARGET_FAILURE;
-		break;
-	case DID_NEXUS_FAILURE:
-		host_status = XEN_VSCSIIF_RSLT_HOST_NEXUS_FAILURE;
-		break;
-	case DID_ALLOC_FAILURE:
-		host_status = XEN_VSCSIIF_RSLT_HOST_ALLOC_FAILURE;
-		break;
-	case DID_MEDIUM_ERROR:
-		host_status = XEN_VSCSIIF_RSLT_HOST_MEDIUM_ERROR;
-		break;
 	case DID_TRANSPORT_MARGINAL:
 		host_status = XEN_VSCSIIF_RSLT_HOST_TRANSPORT_MARGINAL;
 		break;