drm/exynos: Add device tree based discovery support for G2D

This patch adds device tree match table for Exynos G2D controller.

Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>