f2fs: Remove clear_page_private_all()

All callers can simply call folio_detach_private().  This was the
only way that clear_page_private_data() could be called, so remove
that too.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>