tests/kmstest: support exynos

In this patch, to support exynos for KMS, Exynos KMS driver is newly added.
Also, Exynos is added to the list of kmstest supported modules.

Signed-off-by: Hyungwon Hwang <human.hwang@samsung.com>
Signed-off-by: Rob Clark <robclark@freedesktop.org>