tee: add sandbox driver

Adds a sandbox tee driver which emulates a generic TEE with the OP-TEE
AVB TA.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
[trini: Fix printf warnings in ta_avb_invoke_func, slots is uint]
Signed-off-by: Tom Rini <trini@konsulko.com>

include/sandboxtee.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2018 Linaro Limited
+ */
+
+#ifndef __SANDBOXTEE_H
+#define __SANDBOXTEE_H
+
+/**
+ * struct sandbox_tee_state - internal state of the sandbox TEE
+ * @session:	current open session
+ * @num_shms:	number of registered shared memory objects
+ * @ta:		Trusted Application of current session
+ */
+struct sandbox_tee_state {
+	u32 session;
+	int num_shms;
+	void *ta;
+};
+
+#endif /*__SANDBOXTEE_H*/