MINOR: lists: fix indentation.

Fix indentation in the recently added list_to_mt_list().
diff --git a/include/common/mini-clist.h b/include/common/mini-clist.h
index 40baf5d..589a1d9 100644
--- a/include/common/mini-clist.h
+++ b/include/common/mini-clist.h
@@ -676,7 +676,7 @@
 
 static __inline struct mt_list *list_to_mt_list(struct list *list)
 {
-		union {
+	union {
 		struct mt_list *mt_list;
 		struct list *list;
 	} mylist;