Core: change iovec return type to psa_status_t

 - Change the return type of the iovec veneer functions to psa_status_t.
 - Modify TF-M core to forward any return value from secure functions
   that use iovec API to the caller.
 - Update Core test services to use negative return values for
   error, and zero or positive values for successful secure function
   execution.

Change-Id: I5b42a194b955fd003c90d6dfd654ab55be483d20
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>
diff --git a/interface/include/psa_crypto.h b/interface/include/psa_crypto.h
index f122841..0bc8ad3 100644
--- a/interface/include/psa_crypto.h
+++ b/interface/include/psa_crypto.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2019, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -56,28 +56,7 @@
  * @{
  */
 
-#if defined(PSA_SUCCESS)
-/* If PSA_SUCCESS is defined, assume that PSA crypto is being used
- * together with PSA IPC, which also defines the identifier
- * PSA_SUCCESS. We must not define PSA_SUCCESS ourselves in that case;
- * the other error code names don't clash. Also define psa_status_t as
- * an alias for the type used by PSA IPC. This is a temporary hack
- * until we unify error reporting in PSA IPC and PSA crypo.
- *
- * Note that psa_defs.h must be included before this header!
- */
-typedef psa_error_t psa_status_t;
-
-#else /* defined(PSA_SUCCESS) */
-
-/**
- * \brief Function return status.
- *
- * This is either #PSA_SUCCESS (which is zero), indicating success,
- * or a nonzero value indicating that an error occurred. Errors are
- * encoded as one of the \c PSA_ERROR_xxx values defined here.
- */
-typedef int32_t psa_status_t;
+#if !defined(PSA_SUCCESS)
 
 /** The action was completed successfully. */
 #define PSA_SUCCESS ((psa_status_t)0)