drm/tegra: sor: Reset the correct debugfs fields

When tearing down debugfs support, make sure to reset the fields to NULL
in the correct order, otherwise the debugfs root will not be properly
removed.
Signed-off-by: NThierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/sor.c

@@ -861,10 +861,10 @@ static void tegra_sor_debugfs_exit(struct tegra_sor *sor)
 	sor->minor = NULL;
 
 	kfree(sor->debugfs_files);
-	sor->debugfs = NULL;
+	sor->debugfs_files = NULL;
 
 	debugfs_remove_recursive(sor->debugfs);
-	sor->debugfs_files = NULL;
+	sor->debugfs = NULL;
 }
 
 static void tegra_sor_connector_dpms(struct drm_connector *connector, int mode)