ON-17172: Convert page to folio to access index

The offset has changed name in the page struct, but is consistently called index in the folio
struct, so by using the folio we retain compat between versions.

Author: sianj-xilinx

src/lib/kernel_utils/hugetlb.c

@@ -318,7 +318,7 @@ loff_t
 oo_hugetlb_page_offset(struct page *page)
 {
 #ifdef EFRM_HUGETLB_INDEX_BY_PAGE
-	return page->index * PAGE_SIZE;
+	return page_folio(page)->index * PAGE_SIZE;
 #else
 	return page->index * OO_HUGEPAGE_SIZE;
 #endif