mm/filemap: make folio_put_wait_locked static

It's only used in mm/filemap.c, since commit <ffa65753>
("mm/migrate.c: rework migration_entry_wait() to not take a pageref").

Make it static.

Link: https://lkml.kernel.org/r/20220914021738.3228011-1-sunke@kylinos.cnSigned-off-by: Ke Sun <sunke@kylinos.cn>
Reported-by: k2ci <kernel-bot@kylinos.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/pagemap.h

@@ -1039,7 +1039,6 @@ static inline int wait_on_page_locked_killable(struct page *page)
 	return folio_wait_locked_killable(page_folio(page));
 }
 
-int folio_put_wait_locked(struct folio *folio, int state);
 void wait_on_page_writeback(struct page *page);
 void folio_wait_writeback(struct folio *folio);
 int folio_wait_writeback_killable(struct folio *folio);

mm/filemap.c

@@ -1460,7 +1460,7 @@ EXPORT_SYMBOL(folio_wait_bit_killable);
  *
  * Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal.
  */
-int folio_put_wait_locked(struct folio *folio, int state)
+static int folio_put_wait_locked(struct folio *folio, int state)
 {
 	return folio_wait_bit_common(folio, PG_locked, state, DROP);
 }