drm/exynos: added drm prime feature.

this patch adds exynos specific codes for DRM Prime feature.
with this patch, user application can get file descriptor
from gem handle through DRM_IOCTL_PRIME_HANDLE_TO_FD ioctl
command(export) and also gem handle from file descriptor
through DRM_IOCTL_PRIME_FD_TO_HANLDE(import) ioctl command.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/drivers/gpu/drm/exynos/Kconfig b/drivers/gpu/drm/exynos/Kconfig
index 3343ac4..135b618 100644
--- a/drivers/gpu/drm/exynos/Kconfig
+++ b/drivers/gpu/drm/exynos/Kconfig
@@ -10,6 +10,12 @@
 	  Choose this option if you have a Samsung SoC EXYNOS chipset.
 	  If M is selected the module will be called exynosdrm.
 
+config DRM_EXYNOS_DMABUF
+	bool "EXYNOS DRM DMABUF"
+	depends on DRM_EXYNOS
+	help
+	  Choose this option if you want to use DMABUF feature for DRM.
+
 config DRM_EXYNOS_FIMD
 	bool "Exynos DRM FIMD"
 	depends on DRM_EXYNOS && !FB_S3C