btrfs: make btrfs_cleanup_ordered_extents() support large folios

btrfs: make btrfs_cleanup_ordered_extents() support large folios

When hitting a large folio, btrfs_cleanup_ordered_extents() will get the
same large folio multiple times, and clearing the same range again and
again.

Thankfully this is not causing anything wrong, just inefficiency.

This is caused by the fact that we're iterating folios using the old
page index, thus can hit the same large folio again and again.

Enhance it by increasing @index to the index of the folio end, and only
increase @index by 1 if we failed to grab a folio.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>