ARM: H1940: add lcd/backlight device definition

Add lcd and backlight device definition. The pwm backlight stuff does
not allow to really set maximum pwm as with my custom driver but it's
better to use standard driver instead of out of tree driver.

Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
[ben-linux@fluff.org: tidy header]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>