drm/exynos: hdmi: using drm_display_mode timings for exynos4

Exynos5 is already using drm_display_mode for timings parameters. Exynos4
is also modifed to use the same. List of supported resolutions and
corresponding timings are removed which helps is enabling some extra
resolutions. It also cleans some of the duplicate code.

Exynos4 and Exynos5 Mixers, work fine for the same range of resolutions. Hence
same condition (to find the supported mode) is applied to both.

More exynos4 phy configs can be added later to extend the mode supprot.

Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>