[S390] Remove open-coded mem_map usage.

Use page_to_phys and pfn_to_page to avoid open-coded mem_map usage.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/include/asm-s390/pgalloc.h b/include/asm-s390/pgalloc.h
index 803bc70..28619de 100644
--- a/include/asm-s390/pgalloc.h
+++ b/include/asm-s390/pgalloc.h
@@ -116,7 +116,7 @@
 static inline void
 pmd_populate(struct mm_struct *mm, pmd_t *pmd, struct page *page)
 {
-	pmd_populate_kernel(mm, pmd, (pte_t *)((page-mem_map) << PAGE_SHIFT));
+	pmd_populate_kernel(mm, pmd, (pte_t *)page_to_phys(page));
 }
 
 /*