video: Move last_sync to private data

Rather than using a static variable, use the video device's private
data to remember when the last video sync was completed. This allows
each display to have its own sync and avoids using static data in SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/video-uclass.c b/drivers/video/video-uclass.c
index ff1382f..a95b5f1 100644
--- a/drivers/video/video-uclass.c
+++ b/drivers/video/video-uclass.c
@@ -349,6 +349,7 @@
 /* Flush video activity to the caches */
 int video_sync(struct udevice *vid, bool force)
 {
+	struct video_priv *priv = dev_get_uclass_priv(vid);
 	struct video_ops *ops = video_get_ops(vid);
 	int ret;
 
@@ -364,20 +365,15 @@
 	 * out whether it exists? For now, ARM is safe.
 	 */
 #if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)
-	struct video_priv *priv = dev_get_uclass_priv(vid);
-
 	if (priv->flush_dcache) {
 		flush_dcache_range((ulong)priv->fb,
 				   ALIGN((ulong)priv->fb + priv->fb_size,
 					 CONFIG_SYS_CACHELINE_SIZE));
 	}
 #elif defined(CONFIG_VIDEO_SANDBOX_SDL)
-	struct video_priv *priv = dev_get_uclass_priv(vid);
-	static ulong last_sync;
-
-	if (force || get_timer(last_sync) > 100) {
+	if (force || get_timer(priv->last_sync) > 100) {
 		sandbox_sdl_sync(priv->fb);
-		last_sync = get_timer(0);
+		priv->last_sync = get_timer(0);
 	}
 #endif
 	return 0;