drm/gem: free vma-node during object-cleanup

All drivers currently need to clean up the vma-node manually. There is no
fancy logic involved so lets just clean it up unconditionally. The
vma-manager correctly catches multiple calls so we are fine.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>

drivers/gpu/drm/drm_gem.c

@@ -693,6 +693,8 @@ drm_gem_object_release(struct drm_gem_object *obj)
 
 	if (obj->filp)
 		fput(obj->filp);
+
+	drm_gem_free_mmap_offset(obj);
 }
 EXPORT_SYMBOL(drm_gem_object_release);