f2fs: Use a data folio in f2fs_submit_page_bio()

Remove a call to compound_head().  We can call bio_add_folio_nofail()
here because we just allocated the bio, so we know it can't fail and
thus the error path can never be taken.

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