test: video: Provide an easy way to watch video tests

The video tests run past too quickly to see what is going on. Update
them to introduce a delay after each check of the screen contents, when
LOG_DEBUG is enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>

test/dm/video.c

@@ -17,6 +17,7 @@
 #include <asm/sdl.h>
 #include <dm/test.h>
 #include <dm/uclass-internal.h>
+#include <linux/delay.h>
 #include <test/lib.h>
 #include <test/test.h>
 #include <test/ut.h>
@@ -69,6 +70,10 @@ int video_compress_fb(struct unit_test_state *uts, struct udevice *dev,
 	if (ret)
 		return ret;
 
+	/* provide a useful delay if #define LOG_DEBUG at the top of file */
+	if (_DEBUG)
+		mdelay(300);
+
 	return destlen;
 }