Build: Move call of target_add_scatter_file() to NS side

Align with the change in TF-M NS build reference implementation.

Signed-off-by: David Hu <david.hu@arm.com>
Change-Id: I388a20880d8e86e106ae4ab80eb092ca13c985f0
diff --git a/tests_reg/CMakeLists.txt b/tests_reg/CMakeLists.txt
index 1d9f901..bb0f03e 100644
--- a/tests_reg/CMakeLists.txt
+++ b/tests_reg/CMakeLists.txt
@@ -58,3 +58,10 @@
     SUFFIX ".axf"
     RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin"
 )
+
+target_add_scatter_file(tfm_ns ${CONFIG_SPE_PATH}/platform/linker_scripts)
+
+target_link_options(tfm_ns
+    PRIVATE
+        $<$<C_COMPILER_ID:GNU>:-Wl,-Map=${CMAKE_BINARY_DIR}/bin/tfm_ns.map>
+)