Core: Align psa_wait() to PSA FF 1.0.0

If the signal_mask does not include any assigned signals,
it is a PROGRAMMER ERROR, trigger the tfm_panic.

Change-Id: Ib3699800e540a758b79a0a79f55f6c6ba2285187
Signed-off-by: Shawn Shan <shawn.shan@arm.com>
diff --git a/secure_fw/spm/spm_api.h b/secure_fw/spm/spm_api.h
index ce042f7..e1de88d 100644
--- a/secure_fw/spm/spm_api.h
+++ b/secure_fw/spm/spm_api.h
@@ -88,6 +88,7 @@
     uint32_t signals;                   /* Service signals had been triggered*/
     struct tfm_list_node_t service_list;/* Service list                      */
     struct tfm_thrd_ctx sp_thrd;        /* Thread context                    */
+    uint32_t assigned_signals;          /* All assigned signals              */
 #else /* TFM_PSA_API */
     uint32_t partition_state;
     uint32_t caller_partition_idx;