[mutter] crtc-kms: Include MetaCrtc in MetaCrtcKms struct

[Florian Müllner <fmuellner src gnome org>]

commit 19b467aa01798ef530cec6aeb5f3c30600426106
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Jun 11 11:49:47 2020 +0200

    crtc-kms: Include MetaCrtc in MetaCrtcKms struct
    
    Otherwise it can't be a GObject inheriting MetaCrtc. This fixes warning
    logged as
    
    "invalid uninstantiatable type '(null)' in cast to 'MetaCrtcKms'"
    
    Fixes: 1ce9e379d99a8e15b3d043013062104f9b569574
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1308

 src/backends/native/meta-crtc-kms.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/backends/native/meta-crtc-kms.c b/src/backends/native/meta-crtc-kms.c
index 89d6f40a89..ed799cd65d 100644
--- a/src/backends/native/meta-crtc-kms.c
+++ b/src/backends/native/meta-crtc-kms.c
@@ -37,6 +37,8 @@
 
 struct _MetaCrtcKms
 {
+  MetaCrtc parent;
+
   MetaKmsCrtc *kms_crtc;
 
   MetaKmsPlane *primary_plane;