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/[e-mail]
Reviewed-by: Juergen Gross <[e-mail]>
Signed-off-by: Mike Christie <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/xen-scsifront.c

···
 		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

···
 	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;