drm: exynos: remove drm hdmi platform data struct

This patch removes the drm hdmi platform data structure which is no
longer in use by drm hdmi driver after this patch set get merged. s5p
hdmi platform data structure is used instead.

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>