drm/mediatek: hdmi: Add check for CEA modes only

Some SoCs like the MT8167 are not validated and supported for
HDMI modes out of HDMI CEA modes, so add a configuration boolean
to filter out non-CEA modes.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>