Build: Always include preload_ns.cmake if it exists

Rather than using a cmake variable to determine whether to include
preload_ns.cmake, always include it if it exists.

Change-Id: I7c9f4a6d51cc256d2b482c13ecc269b94eb228ac
Signed-off-by: Chris Brand <chris.brand@cypress.com>
diff --git a/test/secure_fw/secure_tests.cmake b/test/secure_fw/secure_tests.cmake
index 9361712..f071623 100644
--- a/test/secure_fw/secure_tests.cmake
+++ b/test/secure_fw/secure_tests.cmake
@@ -1,5 +1,7 @@
 #-------------------------------------------------------------------------------
 # Copyright (c) 2021-2022, Arm Limited. All rights reserved.
+# Copyright (c) 2022 Cypress Semiconductor Corporation (an Infineon company)
+# or an affiliate of Cypress Semiconductor Corporation. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -7,7 +9,7 @@
 
 # Since the main test directory is a NS dir, this subdir is specifically made a
 # secure directory as it build the secure side tests and services
-if (TFM_MULTI_CORE_TOPOLOGY)
+if (EXISTS ${CMAKE_SOURCE_DIR}/platform/ext/target/${TFM_PLATFORM}/preload_ns.cmake)
     include(${CMAKE_SOURCE_DIR}/platform/ext/target/${TFM_PLATFORM}/preload.cmake)
     tfm_toolchain_reload_compiler()
 endif()