Revert "SPM: Add STATUS_NEED_SCHEDULE to manage scheduler"

This reverts commit 9e38935fabf7eae9d54a550bd578163ec9ca1f99.

Reason for revert: Nightly test issue.

Change-Id: I68af7380bd5aa3f9be8363b52b261b1cf310cd59
diff --git a/secure_fw/spm/ffm/interrupt.c b/secure_fw/spm/ffm/interrupt.c
index 0b5e043..7ec611e 100644
--- a/secure_fw/spm/ffm/interrupt.c
+++ b/secure_fw/spm/ffm/interrupt.c
@@ -21,7 +21,6 @@
 
 #include "load/spm_load_api.h"
 #include "ffm/backend.h"
-#include "internal_status_code.h"
 
 extern uintptr_t spm_boundary;
 
@@ -143,7 +142,6 @@
 {
     psa_flih_result_t flih_result;
     struct partition_t *p_part;
-    psa_status_t ret = 0;
 
     if (!p_pt || !p_ildi) {
         tfm_core_panic();
@@ -177,10 +175,10 @@
     }
 
     if (flih_result == PSA_FLIH_SIGNAL) {
-        ret = backend_assert_signal(p_pt, p_ildi->signal);
+        backend_assert_signal(p_pt, p_ildi->signal);
         /* In SFN backend, there is only one thread, no thread switch. */
 #if CONFIG_TFM_SPM_BACKEND_SFN != 1
-        if (ret == STATUS_NEED_SCHEDULE) {
+        if (THRD_EXPECTING_SCHEDULE()) {
             tfm_arch_trigger_pendsv();
         }
 #endif