btrfs: Convert from set_page_dirty to dirty_folio

Optimise the non-DEBUG case to just call filemap_dirty_folio
directly.  The DEBUG case doesn't actually compile, but convert
it to dirty_folio anyway.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Mike Marshall <hubcap@omnibond.com> # orangefs
Tested-by: David Howells <dhowells@redhat.com> # afs