All callers of nilfs_page_buffers_clean() now have a folio, so convert it
to take a folio.  While I'm at it, make it return a bool.

Link: https://lkml.kernel.org/r/20231114084436.2755-6-konishi.ryusuke@gmail.comSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>