SPM: Add runtime SFN backend

A backend for implementing 'SFN'. This runtime backend is selected
if:
- All partitions included in the current build are 'SFN' partitions.
- Isolation level 1.

The configuration is generated by tooling, and output to the
generated file 'config_impl.h'.

Change-Id: I819c78c7a912f86174d102d389a2714ae17e5062
Signed-off-by: Ken Liu <Ken.Liu@arm.com>
Co-authored-by: Mingyang Sun <mingyang.sun@arm.com>
diff --git a/secure_fw/spm/include/ffm/psa_api.h b/secure_fw/spm/include/ffm/psa_api.h
index 6ea3c46..1c78e46 100644
--- a/secure_fw/spm/include/ffm/psa_api.h
+++ b/secure_fw/spm/include/ffm/psa_api.h
@@ -247,14 +247,16 @@
  * \param[in] status            Message result value to be reported to the
  *                              client.
  *
- * \retval void                 Success.
+ * \retval Positive integer     Success, the connection handle.
+ * \retval PSA_SUCCESS          Success
  * \retval "PROGRAMMER ERROR"   The call is invalid, one or more of the
  *                              following are true:
  * \arg                         msg_handle is invalid.
  * \arg                         An invalid status code is specified for the
  *                              type of message.
  */
-void tfm_spm_partition_psa_reply(psa_handle_t msg_handle, psa_status_t status);
+int32_t tfm_spm_partition_psa_reply(psa_handle_t msg_handle,
+                                    psa_status_t status);
 
 /**
  * \brief Function body of \ref psa_norify.