btrfs: Remove a use of PAGE_SIZE in btrfs_invalidate_folio()

While btrfs doesn't use large folios yet, this should have been changed
as part of the conversion from invalidatepage to invalidate_folio.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>

fs/btrfs/inode.c

@@ -8296,7 +8296,7 @@ static void btrfs_invalidate_folio(struct folio *folio, size_t offset,
 	 * cover the full folio, like invalidating the last folio, we're
 	 * still safe to wait for ordered extent to finish.
 	 */
-	if (!(offset == 0 && length == PAGE_SIZE)) {
+	if (!(offset == 0 && length == folio_size(folio))) {
 		btrfs_releasepage(&folio->page, GFP_NOFS);
 		return;
 	}