From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

Now that atomic modesetting is implemented for exynos enable the
DRIVER_ATOMIC flag on the driver's features.
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Inki Dae <inki.dae@samsung.com>