video: Rename CONFIG_DM_VIDEO to CONFIG_VIDEO

Now that all the old code is gone, rename this option. Driver model
migration is now complete.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/serial/sandbox.c b/drivers/serial/sandbox.c
index f122e3f..f400381 100644
--- a/drivers/serial/sandbox.c
+++ b/drivers/serial/sandbox.c
@@ -139,7 +139,7 @@
 		return 0;
 
 	os_usleep(100);
-	if (IS_ENABLED(CONFIG_DM_VIDEO) && !IS_ENABLED(CONFIG_SPL_BUILD))
+	if (IS_ENABLED(CONFIG_VIDEO) && !IS_ENABLED(CONFIG_SPL_BUILD))
 		video_sync_all();
 	avail = membuff_putraw(&priv->buf, 100, false, &data);
 	if (!avail)