mm/page_alloc: add __init annotations to init_mem_debugging_and_hardening()

It's only called by mm_init(). Add __init annotations to it.

Link: https://lkml.kernel.org/r/20220916072257.9639-6-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm.h

@@ -3092,7 +3092,7 @@ extern int apply_to_existing_page_range(struct mm_struct *mm,
 				   unsigned long address, unsigned long size,
 				   pte_fn_t fn, void *data);
 
-extern void init_mem_debugging_and_hardening(void);
+extern void __init init_mem_debugging_and_hardening(void);
 #ifdef CONFIG_PAGE_POISONING
 extern void __kernel_poison_pages(struct page *page, int numpages);
 extern void __kernel_unpoison_pages(struct page *page, int numpages);

mm/page_alloc.c

@@ -903,7 +903,7 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
  * order of appearance. So we need to first gather the full picture of what was
  * enabled, and then make decisions.
  */
-void init_mem_debugging_and_hardening(void)
+void __init init_mem_debugging_and_hardening(void)
 {
 	bool page_poisoning_requested = false;