s390/mm: use CRST_ALLOC_ORDER instead of number

Use CRST_ALLOC_ORDER to make it more obvious what the order means,
and also to be consistent with other code, e.g. the vmemmap code.
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/mm/pgalloc.c

@@ -53,17 +53,17 @@ __initcall(page_table_register_sysctl);
 
 unsigned long *crst_table_alloc(struct mm_struct *mm)
 {
-	struct page *page = alloc_pages(GFP_KERNEL, 2);
+	struct page *page = alloc_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
 
 	if (!page)
 		return NULL;
-	arch_set_page_dat(page, 2);
+	arch_set_page_dat(page, CRST_ALLOC_ORDER);
 	return (unsigned long *) page_to_virt(page);
 }
 
 void crst_table_free(struct mm_struct *mm, unsigned long *table)
 {
-	free_pages((unsigned long) table, 2);
+	free_pages((unsigned long)table, CRST_ALLOC_ORDER);
 }
 
 static void __crst_table_upgrade(void *arg)
@@ -403,7 +403,7 @@ void __tlb_remove_table(void *_table)
 
 	switch (half) {
 	case 0x00U:	/* pmd, pud, or p4d */
-		free_pages((unsigned long) table, 2);
+		free_pages((unsigned long)table, CRST_ALLOC_ORDER);
 		return;
 	case 0x01U:	/* lower 2K of a 4K page table */
 	case 0x02U:	/* higher 2K of a 4K page table */