drm/exynos: mic: Add mode_set callback function

drm/exynos: mic: Add mode_set callback function

Before applying the patch, used the of_get_videomode function to
parse the display-timings in the panel which is the child driver
of dsi in the devicetree. this is wrong. So removed the
of_get_videomode and fixed to get videomode struct through
mode_set callback function.

Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>