sandbox: Slow down the LCD sync rate

There is seldom a need to refresh at 100Hz and it uses a lot of CPU.
Reduce the rate to 10Hz which seems to be adequate.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/video-uclass.c b/drivers/video/video-uclass.c
index 7d499bc..5215114 100644
--- a/drivers/video/video-uclass.c
+++ b/drivers/video/video-uclass.c
@@ -204,7 +204,7 @@
 	struct video_priv *priv = dev_get_uclass_priv(vid);
 	static ulong last_sync;
 
-	if (force || get_timer(last_sync) > 10) {
+	if (force || get_timer(last_sync) > 100) {
 		sandbox_sdl_sync(priv->fb);
 		last_sync = get_timer(0);
 	}