auxdisplay/ht16k33.c: Convert to use vm_map_pages_zero()

While using mmap, the incorrect values of length and vm_pgoff are
ignored and this driver goes ahead with mapping fbdev.buffer
to user vma.

Convert vm_insert_pages() to use vm_map_pages_zero(). We could later
"fix" these drivers to behave according to the normal vm_pgoff
offsetting simply by removing the _zero suffix on the function name
and if that causes regressions, it gives us an easy way to revert.
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Acked-by: Robin van der Gracht <robin@protonic.nl>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

drivers/auxdisplay/ht16k33.c

@@ -223,9 +223,9 @@ static const struct backlight_ops ht16k33_bl_ops = {
 static int ht16k33_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
 	struct ht16k33_priv *priv = info->par;
+	struct page *pages = virt_to_page(priv->fbdev.buffer);
 
-	return vm_insert_page(vma, vma->vm_start,
-			      virt_to_page(priv->fbdev.buffer));
+	return vm_map_pages_zero(vma, &pages, 1);
 }
 
 static struct fb_ops ht16k33_fb_ops = {