fbdev: update after backlight argument change

Update the frambuffer drivers to the backlight_device_registers changes.

Signed-off-by: James Simmons <jsimmons@infradead.org>
Cc: Luming Yu <Luming.yu@intel.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>