mm: unexport page_init_poison

page_init_poison is only used in core MM code, so unexport it.

Link: https://lkml.kernel.org/r/20220207063446.1833404-1-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

mm/debug.c

@@ -265,5 +265,4 @@ void page_init_poison(struct page *page, size_t size)
 	if (page_init_poisoning)
 		memset(page, PAGE_POISON_PATTERN, size);
 }
-EXPORT_SYMBOL_GPL(page_init_poison);
 #endif		/* CONFIG_DEBUG_VM */