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/spd/tspd/tspd_common.c b/services/spd/tspd/tspd_common.c
index b806543..fcc2765 100644
--- a/services/spd/tspd/tspd_common.c
+++ b/services/spd/tspd/tspd_common.c
@@ -37,7 +37,7 @@
 #include <bl_common.h>
 #include <runtime_svc.h>
 #include <context_mgmt.h>
-#include <tspd_private.h>
+#include "tspd_private.h"
 
 /*******************************************************************************
  * Given a secure payload entrypoint, register width, cpu id & pointer to a