mm: unexport {,un}lock_page_memcg

These are only used in built-in core mm code.

Link: https://lkml.kernel.org/r/20210820095815.445392-3-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2063,7 +2063,6 @@ void lock_page_memcg(struct page *page)
 {
 	folio_memcg_lock(page_folio(page));
 }
-EXPORT_SYMBOL(lock_page_memcg);
 
 static void __folio_memcg_unlock(struct mem_cgroup *memcg)
 {
@@ -2096,7 +2095,6 @@ void unlock_page_memcg(struct page *page)
 {
 	folio_memcg_unlock(page_folio(page));
 }
-EXPORT_SYMBOL(unlock_page_memcg);
 
 struct obj_stock {
 #ifdef CONFIG_MEMCG_KMEM