auxdisplay/cfag12864bfb.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 cfag12864b_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>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

drivers/auxdisplay/cfag12864bfb.c

@@ -52,8 +52,9 @@ static const struct fb_var_screeninfo cfag12864bfb_var = {
 
 static int cfag12864bfb_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
-	return vm_insert_page(vma, vma->vm_start,
-		virt_to_page(cfag12864b_buffer));
+	struct page *pages = virt_to_page(cfag12864b_buffer);
+
+	return vm_map_pages_zero(vma, &pages, 1);
 }
 
 static struct fb_ops cfag12864bfb_ops = {