kmssink: Add new entry for Xilinx DRM Driver

This adds entry for new DRM driver from xilinx
called "xlnx" which supports atomic modesetting.

We have kept entry for older DRM driver "xilinx_drm"
for backward compatility with a note describing
deprecation.

Signed-off-by: Devarsh Thakkar <devarsht@xilinx.com>

https://bugzilla.gnome.org/show_bug.cgi?id=795228
diff --git a/sys/kms/gstkmssink.c b/sys/kms/gstkmssink.c
index 4991ee3..88ef42e 100644
--- a/sys/kms/gstkmssink.c
+++ b/sys/kms/gstkmssink.c
@@ -168,7 +168,8 @@
 {
   static const char *drivers[] = { "i915", "radeon", "nouveau", "vmwgfx",
     "exynos", "amdgpu", "imx-drm", "rockchip", "atmel-hlcdc", "msm",
-    "xilinx_drm", "vc4", "meson", "sun4i-drm",
+    "xlnx", "vc4", "meson", "sun4i-drm",
+    "xilinx_drm",               /* DEPRECATED. Replaced by xlnx */
   };
   int i, fd = -1;