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: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/gpu/drm/tegra/sor.c b/drivers/gpu/drm/tegra/sor.c
index 18b4d89..bad63d0 100644
--- a/drivers/gpu/drm/tegra/sor.c
+++ b/drivers/gpu/drm/tegra/sor.c
@@ -861,10 +861,10 @@
 	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)