mm/huge_memory: fix comment of page_deferred_list

The current comment is confusing because if global or memcg deferred list
in the second tail page is occupied by compound_head, why we still use
page[2].deferred_list here? I think it wants to say that Global or memcg
deferred list in the first tail page is occupied by compound_mapcount and
compound_pincount so we use the second tail page's deferred_list instead.

Link: https://lkml.kernel.org/r/20220704132201.14611-14-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/huge_mm.h

@@ -294,8 +294,8 @@ static inline bool thp_migration_supported(void)
 static inline struct list_head *page_deferred_list(struct page *page)
 {
 	/*
-	 * Global or memcg deferred list in the second tail pages is
-	 * occupied by compound_head.
+	 * See organization of tail pages of compound page in
+	 * "struct page" definition.
 	 */
 	return &page[2].deferred_list;
 }