drm: exynos: hdmi: replace is_v13 with version check in hdmi

This patch removed the is_v13 variable from the hdmi driver context.
It is replaced with condition check for the hdmi version. This cleans
the way for handling further hdmi versions.

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