drm/exynos: fix flags in dma buf exporting

This patch fixes flags passed to dma buf exporting.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Kyungmin.park <kyungmin.park@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>