Backlight control support for the PXA fram buffer.

Signed-off-by: Rodolfo Giometti <giometti@enneenne.com>

---

Each platform should define the backlight properties in its own setup
file in "linux/arch/arm/mach-pxa/" as follow:

   static int pxafb_bl_get_brightness(struct backlight_device *bl_dev)
   {
   	return read_the_backlight_brightness();
   }

   static int pxafb_bl_update_status(struct backlight_device *bl_dev)
   {
           int perc, ret;

           if (bl_dev->props->power != FB_BLANK_UNBLANK ||
               bl_dev->props->fb_blank != FB_BLANK_UNBLANK)
                   perc = 0;
           else
                   perc = bl_dev->props->brightness;

   	write_the_backlight_brightness(perc);

           return 0;
   }

   static struct backlight_properties wwpc1100_backlight_props = {
           .get_brightness         = pxafb_bl_get_brightness,
           .update_status          = pxafb_bl_update_status,
           .max_brightness         = 100,
   };
      
and then seting up the fb info as follow:

   wwpc1100_pxafb_info.modes = &special_modes;
   wwpc1100_pxafb_info.bl_props = &wwpc1100_backlight_props;
   set_pxa_fb_info(&wwpc1100_pxafb_info);