The vboxvideo module is deprecated.
Do not build it when VBOX_NO_LEGACY_XORG_X11 is defined.

--- a/src/VBox/Additions/linux/drm/Makefile.kmk
+++ b/src/VBox/Additions/linux/drm/Makefile.kmk
@@ -25,6 +25,8 @@
 # SPDX-License-Identifier: GPL-3.0-only
 #
 
+ifndef VBOX_NO_LEGACY_XORG_X11
+
 SUB_DEPTH = ../../../../..
 include $(KBUILD_PATH)/subheader.kmk
 
@@ -50,3 +52,4 @@
 
 include $(FILE_KBUILD_SUB_FOOTER)
 
+endif