buffer: use b_folio in mark_buffer_dirty()

Removes about four calls to compound_head().  Two of them are inline which
removes 132 bytes from the kernel text.

Link: https://lkml.kernel.org/r/20221215214402.3522366-8-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>