exynos: video: Convert several boards to driver model for video

Update several boards to use driver model for video. This involves changes
to the EDP and FIMD (frame buffer) drivers. Existing PWM, simple-panel and
pwm-backlight drivers are used. These work without additional configuration
since they use the device tree settings in the same way as Linux.

Boards converted are:
- snow
- spring
- peach-pit
- peach-pi

All have been tested. Not converted:

- MIPI display driver
- s5pc210_universal
- smdk5420
- smdk5250
- trats
- trats2

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