video: Support showing the U-Boot logo

Show the U-Boot logo by default. This is only 7KB in size so seems like
a useful default for boards that enable a display.

If SPLASH_SCREEN is enabled, it is not enabled by default, so as not to
conflict with that feature.

Also disable it for tests, since we don't want to complicate the output.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/video.h b/include/video.h
index 471b659..1d75a90 100644
--- a/include/video.h
+++ b/include/video.h
@@ -30,12 +30,14 @@
  * @base: Base address of frame buffer, 0 if not yet known
  * @copy_base: Base address of a hardware copy of the frame buffer. See
  *	CONFIG_VIDEO_COPY.
+ * @hide_logo: Hide the logo (used for testing)
  */
 struct video_uc_plat {
 	uint align;
 	uint size;
 	ulong base;
 	ulong copy_base;
+	bool hide_logo;
 };
 
 enum video_polarity {