Dualcpu: Fix NS mailbox linking error

A quick workaround to fix NS mailbox linking error which is caused by
missing tfm_ns_mailbox_tx_stats_init.

Signed-off-by: David Hu <david.hu@arm.com>
Change-Id: I18562b6a793aaf919a0099ee6f45fbb7b5b4a918
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0594e98..469e4ac 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -36,8 +36,8 @@
 if(TFM_PSA_API)
     add_subdirectory(suites/ipc)
 endif()
-if(TFM_MULTI_CORE_TOPOLOGY)
-    add_subdirectory(suites/multi_core)
+if(TFM_MULTI_CORE_TOPOLOGY AND TEST_NS)
+    add_subdirectory(suites/multi_core/non_secure)
 endif()
 
 if (TFM_FUZZER_TOOL_TESTS)
diff --git a/test/suites/multi_core/CMakeLists.txt b/test/suites/multi_core/non_secure/CMakeLists.txt
similarity index 92%
rename from test/suites/multi_core/CMakeLists.txt
rename to test/suites/multi_core/non_secure/CMakeLists.txt
index 696e3f5..b5b66ee 100644
--- a/test/suites/multi_core/CMakeLists.txt
+++ b/test/suites/multi_core/non_secure/CMakeLists.txt
@@ -15,12 +15,12 @@
 
 target_sources(tfm_test_suite_multi_core_ns
     PRIVATE
-        non_secure/multi_core_ns_interface_testsuite.c
+        multi_core_ns_interface_testsuite.c
 )
 
 target_include_directories(tfm_test_suite_multi_core_ns
     PUBLIC
-        non_secure
+        ./
 )
 
 target_compile_definitions(tfm_test_suite_multi_core_ns