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/psci/psci_main.c b/services/std_svc/psci/psci_main.c
index c90929d..8692adf 100644
--- a/services/std_svc/psci/psci_main.c
+++ b/services/std_svc/psci/psci_main.c
@@ -34,10 +34,10 @@
 #include <arch_helpers.h>
 #include <console.h>
 #include <platform.h>
-#include <psci_private.h>
 #include <runtime_svc.h>
 #include <debug.h>
 #include <context_mgmt.h>
+#include "psci_private.h"
 
 /*******************************************************************************
  * PSCI frontend api for servicing SMCs. Described in the PSCI spec.