drm/tegra: sor - Recursively remove debugfs tree

Removing only the root directory will fail when there are still files in
it. Instead of manually removing all files, remove the whole directory
recursively.

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 5c67d97..06f8009 100644
--- a/drivers/gpu/drm/tegra/sor.c
+++ b/drivers/gpu/drm/tegra/sor.c
@@ -1036,7 +1036,7 @@
 
 static int tegra_sor_debugfs_exit(struct tegra_sor *sor)
 {
-	debugfs_remove(sor->debugfs);
+	debugfs_remove_recursive(sor->debugfs);
 	sor->debugfs = NULL;
 
 	return 0;