App: Update test thread stack configuration

Remove user provided memory for stack used by test main thread.

This enables usage of FreeRTOS on the non-secure side to run the tests.
FreeRTOS requires that memory for thread control block and stack is
either user provided or provided by the system (cannot be mixed).

Signed-off-by: Robert Rostohar <Robert.Rostohar@arm.com>
Change-Id: I43ffd914d765bbda89dd10cd2bfa83fcb2be7791
diff --git a/app/main_ns.c b/app/main_ns.c
index 5c424c3..b3a027e 100644
--- a/app/main_ns.c
+++ b/app/main_ns.c
@@ -62,24 +62,17 @@
  */
 #if defined(TEST_FRAMEWORK_NS) || defined(TEST_FRAMEWORK_S) \
  || defined(PSA_API_TEST_NS)
-static uint64_t test_app_stack[(4u * 1024u) / (sizeof(uint64_t))]; /* 4KB */
 static const osThreadAttr_t thread_attr = {
     .name = "test_thread",
-    .stack_mem = test_app_stack,
-    .stack_size = sizeof(test_app_stack),
+    .stack_size = 4096U
 };
 #endif
 
 #ifdef TFM_MULTI_CORE_NS_OS_MAILBOX_THREAD
 static osThreadFunc_t mailbox_thread_func = tfm_ns_mailbox_thread_runner;
-/* 1KB stack */
-#define MAILBOX_THREAD_STACK_SIZE           (1u * 1024u)
-static uint64_t mailbox_thread_stack[MAILBOX_THREAD_STACK_SIZE /
-                                     sizeof(uint64_t)];
 static const osThreadAttr_t mailbox_thread_attr = {
     .name = "mailbox_thread",
-    .stack_mem = mailbox_thread_stack,
-    .stack_size = sizeof(mailbox_thread_stack),
+    .stack_size = 1024U
 };
 #endif