psa-client-server: move psasim from framework repo to the mbedtls one

This is a temporary fix that will be reverted once the framework
repository will have CI checks.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/psa-client-server/psasim/src/common.c b/tests/psa-client-server/psasim/src/common.c
new file mode 100644
index 0000000..287bb50
--- /dev/null
+++ b/tests/psa-client-server/psasim/src/common.c
@@ -0,0 +1,8 @@
+/* Common code between clients and services */
+
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#include "psa/common.h"