Make use of user/system includes more consistent

Make codebase consistent in its use of #include "" syntax for
user includes and #include <> syntax for system includes.

Fixes ARM-software/tf-issues#65

Change-Id: If2f7c4885173b1fd05ac2cde5f1c8a07000c7a33
diff --git a/services/std_svc/std_svc_setup.c b/services/std_svc/std_svc_setup.c
index 080836a..7d5527a 100644
--- a/services/std_svc/std_svc_setup.c
+++ b/services/std_svc/std_svc_setup.c
@@ -34,8 +34,8 @@
 #include <runtime_svc.h>
 #include <std_svc.h>
 #include <psci.h>
-#include <psci_private.h>
 #include <debug.h>
+#include "psci/psci_private.h"
 
 /* Standard Service UUID */
 DEFINE_SVC_UUID(arm_svc_uid,