sd: Fix missing ATO tag check

3aec2f41 introduced a merge error where we would end up check for
sdkp instead of sdkp->ATO. Fix this so we register app tag capability
correctly.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: <stable@vger.kernel.org> # v3.17+
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

drivers/scsi/sd_dif.c

@@ -77,7 +77,7 @@ void sd_dif_config_host(struct scsi_disk *sdkp)
 
 		disk->integrity->flags |= BLK_INTEGRITY_DEVICE_CAPABLE;
 
-		if (!sdkp)
+		if (!sdkp->ATO)
 			return;
 
 		if (type == SD_DIF_TYPE3_PROTECTION)