drm/exynos: do not use mode_set_base function directly

This patch adds exynos_drm_crtc_mode_set_commit function
to update mode data and it makes page flip call this function
instead of calling exynos_drm_crtc_mode_set_base function directly.

exynos_drm_crtc_mode_set_base function is called by drm subsystem
as a callback so we don't have to call this function directly.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>