filemap: Remove lock_page_killable()

There are no more callers; remove this function before any more appear.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

include/linux/pagemap.h

@@ -977,16 +977,6 @@ static inline int folio_lock_killable(struct folio *folio)
 	return 0;
 }
 
-/*
- * lock_page_killable is like lock_page but can be interrupted by fatal
- * signals.  It returns 0 if it locked the page and -EINTR if it was
- * killed while waiting.
- */
-static inline int lock_page_killable(struct page *page)
-{
-	return folio_lock_killable(page_folio(page));
-}
-
 /*
  * folio_lock_or_retry - Lock the folio, unless this would block and the
  * caller indicated that it can handle a retry.