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/boot/pxe_utils.c b/boot/pxe_utils.c
index 3fdd14d..8133006 100644
--- a/boot/pxe_utils.c
+++ b/boot/pxe_utils.c
@@ -1518,7 +1518,7 @@
 		/* display BMP if available */
 		if (cfg->bmp) {
 			if (get_relfile(ctx, cfg->bmp, image_load_addr, NULL)) {
-#if defined(CONFIG_DM_VIDEO)
+#if defined(CONFIG_VIDEO)
 				struct udevice *dev;
 
 				err = uclass_first_device_err(UCLASS_VIDEO, &dev);