Interface: Add psa/error.h header

Adds the psa/error.h header to the interface/include directory. Removes
definitions from psa/client.h that are now in psa/error.h. Fixes
includes for psa/client.h and psa/service.h so that each one includes
exactly the headers it depends on.

Change-Id: Icf6ae904977a4646f33202edb7d6842c2bc5b5cf
Signed-off-by: Jamie Fox <jamie.fox@arm.com>
diff --git a/interface/include/psa/service.h b/interface/include/psa/service.h
index 2e8558a..9af3f67 100644
--- a/interface/include/psa/service.h
+++ b/interface/include/psa/service.h
@@ -8,14 +8,16 @@
 #ifndef __PSA_SERVICE_H__
 #define __PSA_SERVICE_H__
 
+#include <stddef.h>
+#include <stdint.h>
+
+#include "psa/error.h"
+#include "psa/client.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <inttypes.h>
-
-#include "psa/client.h"
-
 /********************** PSA Secure Partition Macros and Types ****************/
 
 /* PSA wait timeouts */