Revert "drm/sun4i: Remove R40 display pipeline compatibles"

This reverts commit 3510e7a7f9.

During the 4.19 merge window for drm-misc, two patches critical to
supporting the display pipeline on the Allwinner R40 SoC were missed.
They were applied later but missed the merge window deadline. As a
result 4.19-rc1 kernel would crash on the R40 when it couldn't parse
the new device tree structure. We ended up removing support for the
R40 display pipeline for 4.19.

Since the missing patches are already merged for 4.20, we can now
revert the commit that removed support.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180921142743.8711-1-wens@csie.org

drivers/gpu/drm/sun4i/sun4i_drv.c

@@ -402,6 +402,7 @@ static const struct of_device_id sun4i_drv_of_table[] = {
 	{ .compatible = "allwinner,sun8i-a33-display-engine" },
 	{ .compatible = "allwinner,sun8i-a83t-display-engine" },
 	{ .compatible = "allwinner,sun8i-h3-display-engine" },
+	{ .compatible = "allwinner,sun8i-r40-display-engine" },
 	{ .compatible = "allwinner,sun8i-v3s-display-engine" },
 	{ .compatible = "allwinner,sun9i-a80-display-engine" },
 	{ .compatible = "allwinner,sun50i-a64-display-engine" },