nilfs2: convert nilfs_copy_page() to nilfs_copy_folio()

nilfs2: convert nilfs_copy_page() to nilfs_copy_folio()

Both callers already have a folio, so pass it in and use it directly.
Removes a lot of hidden calls to compound_head().

Link: https://lkml.kernel.org/r/20231016201114.1928083-13-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>