drm/exynos: Use struct drm_mode_fb_cmd2

The exynos drm also should use struct drm_mode_fb_cmd2 by changes of
308e5bcb commit(drm: add an fb creation
ioctl that takes a pixel format v5).

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>