drm/exynos: mixer: set correct mode for range of resolutions

With this patch, mixer driver find the correct resolution mode for
the range of resolutions, upto 1080 vertical lines. Resolution will
be categorized to NTSC SD, PAL SD or HD and the correct mode is
set to the mixer configuration register.

Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>