os_test: get client identity

Add helper method to query current client identity for session login
testing.

Acked-by: Etienne Carriere <etienne.carriere@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Jerome Forissier <jerome@forissier.org>
Signed-off-by: Vesa Jääskeläinen <vesa.jaaskelainen@vaisala.com>
diff --git a/ta/os_test/include/os_test.h b/ta/os_test/include/os_test.h
index 6c3d4c4..88124f0 100644
--- a/ta/os_test/include/os_test.h
+++ b/ta/os_test/include/os_test.h
@@ -48,5 +48,6 @@
 TEE_Result ta_entry_call_lib_dl(uint32_t param_types, TEE_Param params[4]);
 TEE_Result ta_entry_call_lib_dl_panic(uint32_t param_types, TEE_Param params[4]);
 TEE_Result ta_entry_get_global_var(uint32_t param_types, TEE_Param params[4]);
+TEE_Result ta_entry_client_identity(uint32_t param_types, TEE_Param params[4]);
 
 #endif /*OS_TEST_H */