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_afflvl_off.c b/services/std_svc/psci/psci_afflvl_off.c
index f6bd40c..0598f42 100644
--- a/services/std_svc/psci/psci_afflvl_off.c
+++ b/services/std_svc/psci/psci_afflvl_off.c
@@ -36,7 +36,7 @@
 #include <console.h>
 #include <platform.h>
 #include <psci.h>
-#include <psci_private.h>
+#include "psci_private.h"
 
 typedef int (*afflvl_off_handler)(unsigned long, aff_map_node *);