dm: lcd: Avoid using the lcd.h header file with driver model

The LCD functions and definitions are not used with the driver model video
uclass. When all boards are converted over we can remove the file. For now,
use #ifdef to omit the contents.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Anatolij Gustschin <agust@denx.de>