mm: add nommu variant of vm_insert_pages()

An identical one exists for vm_insert_page(), add one for
vm_insert_pages() to avoid needing to check for CONFIG_MMU in code using
it.
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

mm/nommu.c

@@ -355,6 +355,13 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
 }
 EXPORT_SYMBOL(vm_insert_page);
 
+int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
+			struct page **pages, unsigned long *num)
+{
+	return -EINVAL;
+}
+EXPORT_SYMBOL(vm_insert_pages);
+
 int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
 			unsigned long num)
 {