drm/exynos: fix module build error

This patch removes all MODULE_DEVICE_TABLE declarations.

Exynos drm drivers don't need to create MODULE_DEVICE_TABLE
yet because all devices of Exynos drm include in one SoC so
they cannot be plugged in as of now.

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