AuditLog: Non Secure interface

-- Add the NS API interface and related SVC functions
   for the Audit Logging secure service.
-- Modify the example application to support the new
   NS interface for the Audit Logging secure service.

Change-Id: I6158742585db19b58e45704f13a4e5b1b4557d69
Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
diff --git a/interface/include/tfm_ns_svc.h b/interface/include/tfm_ns_svc.h
index 4e4d731..b40b7c0 100644
--- a/interface/include/tfm_ns_svc.h
+++ b/interface/include/tfm_ns_svc.h
@@ -45,7 +45,8 @@
     X(SVC_TFM_SST_GET_ATTRIBUTES, tfm_sst_svc_get_attributes) \
     X(SVC_TFM_SST_READ, tfm_sst_svc_read) \
     X(SVC_TFM_SST_WRITE, tfm_sst_svc_write) \
-    X(SVC_TFM_SST_DELETE, tfm_sst_svc_delete)
+    X(SVC_TFM_SST_DELETE, tfm_sst_svc_delete) \
+    X(SVC_TFM_LOG_RETRIEVE, NULL)
 
 /**
  * \def LIST_SVC_CORE_TEST_INTERACTIVE