Add backlight dimmer option

This is based on n5dim by @mzhou  https://github.com/mzhou/n5dim
fix for app-mounted directories (thanks @mkasick)

Signed-off-by: flar2 <asegaert@gmail.com>
Defconfig: Correct Kernel Version Header

* I'm being picky here

Signed-off-by: Chester Kener <Cl3Kener@gmail.com>