drm: exynos: hdmi: support for platform variants

This patch implements check if HDMI is version 1.3 by using a driver variant
instead of platform data.

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