video: backlight: aat2870_bl: update driver to newer version

The older driver uses the function 'gpio_configure' which was removed from kernel source (2.6.37)

Change-Id: Ic67b8a22a69d2a9c7a199bc34d318941ba676531
Signed-off-by: Randolf Kastenmaier <randolf.kastenmaier@gmail.com>