exynos: video: Drop old unused code

Now that we are using driver model, we can drop the weak functions and LCD
init in the board file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>