drm/exynos: set buffer type from exporter.

when fd is imported to gem, whether the memory type from exporter
is contigous or not should be set to gem flag so that drm-based
driver can aware of the memory type.

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