xen-scsiback: Fix compile warning for 64-bit LUN

drivers/xen/xen-scsiback.c: In function ‘scsiback_add_translation_entry’:
drivers/xen/xen-scsiback.c:911:3: warning: format ‘%d’ expects argument of type ‘int’, but argument 3 has type ‘long long unsigned int’ [-Wformat]

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 10d6780..823bdf4 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -908,7 +908,7 @@
 	mutex_unlock(&scsiback_mutex);
 
 	if (!tpg) {
-		pr_err("%s:%d %s\n", phy, unpacked_lun, error);
+		pr_err("%s:%llu %s\n", phy, unpacked_lun, error);
 		return -ENODEV;
 	}