[SPM] tidying common code to tftf and cactus

This patch moves the code used to test SPM functionality, not explicitly
described in FF-A specification, from ffa_helpers to spm_common which is
built for both tftf and cactus.

Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>
Change-Id: I461efad977cc4d02701feea7b2215a61453716ef
diff --git a/tftf/tests/common/test_helpers.c b/tftf/tests/common/test_helpers.c
index 05b09d7..d794beb 100644
--- a/tftf/tests/common/test_helpers.c
+++ b/tftf/tests/common/test_helpers.c
@@ -1,11 +1,10 @@
 /*
- * Copyright (c) 2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2020-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
 #include <arch_helpers.h>
-#include <ffa_helpers.h>
 #include <plat_topology.h>
 #include <platform.h>
 #include <power_management.h>