f2fs: remove folio_detach_private() in .invalidate_folio and .release_folio

We have maintain PagePrivate and page_private and page reference
w/ {set,clear}_page_private_*, it doesn't need to call
folio_detach_private() in the end of .invalidate_folio and
.release_folio, remove it and use f2fs_bug_on instead.

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>