hugetlb: Convert huge_add_to_page_cache() to use a folio

Remove the last caller of add_to_page_cache()

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>