sandbox: video: Speed up video output

At present there are many situations where sandbox syncs the display to
the SDL frame buffer. This is a very expensive operation but is only
needed every now and then. Update video_sync() so that we can specify
whether this operation is really needed.

At present this flag is not used on other architectures. It could also
be used for reducing writeback-cache flushes but the benefit of that would
need to be investigated.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
diff --git a/drivers/video/vidconsole-uclass.c b/drivers/video/vidconsole-uclass.c
index 7f95e9c..89ac8b3 100644
--- a/drivers/video/vidconsole-uclass.c
+++ b/drivers/video/vidconsole-uclass.c
@@ -86,7 +86,7 @@
 		if (priv->ycur < 0)
 			priv->ycur = 0;
 	}
-	video_sync(dev->parent);
+	video_sync(dev->parent, false);
 
 	return 0;
 }
@@ -113,7 +113,7 @@
 	}
 	priv->last_ch = 0;
 
-	video_sync(dev->parent);
+	video_sync(dev->parent, false);
 }
 
 static const struct vid_rgb colors[VID_COLOR_COUNT] = {
@@ -293,7 +293,7 @@
 
 		if (mode == 2) {
 			video_clear(dev->parent);
-			video_sync(dev->parent);
+			video_sync(dev->parent, false);
 			priv->ycur = 0;
 			priv->xcur_frac = priv->xstart_frac;
 		} else {
@@ -449,7 +449,7 @@
 	struct udevice *dev = sdev->priv;
 
 	vidconsole_put_char(dev, ch);
-	video_sync(dev->parent);
+	video_sync(dev->parent, false);
 }
 
 static void vidconsole_puts(struct stdio_dev *sdev, const char *s)
@@ -458,7 +458,7 @@
 
 	while (*s)
 		vidconsole_put_char(dev, *s++);
-	video_sync(dev->parent);
+	video_sync(dev->parent, false);
 }
 
 /* Set up the number of rows and colours (rotated drivers override this) */
@@ -547,7 +547,7 @@
 	for (s = argv[1]; *s; s++)
 		vidconsole_put_char(dev, *s);
 
-	video_sync(dev->parent);
+	video_sync(dev->parent, false);
 
 	return 0;
 }