libdrm: add exynos drm support

this patch adds libdrm_exynos helper layer that inclues some intefaces
for exynos specific gem and virtual display driver and also adds exynos
module name to modtest and vbltest.

Changelog v2:
- fixed exynos broken ioctl.
  the pointer of uint64_t *edid should be removed.
- removed unnecessary definitions.
- added drm prime interfaces.
  this feature is used to share a buffer between drivers or memory managers
  and for this, please, refer to below links:
	http://www.mjmwired.net/kernel/Documentation/dma-buf-sharing.txt
	http://lwn.net/Articles/488664/

this patch is based on a link below:
	git://anongit.freedesktop.org/mesa/drm


	commit id: d72a44c7

Reviewed-by: Rob Clark <rob@ti.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Rob Clark <rob@ti.com>