mm: convert do_swap_page() to use swap_cache_get_folio()

Saves a folio->page->folio conversion.

Link: https://lkml.kernel.org/r/20220902194653.1739778-38-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>