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_helpers.S b/services/spd/tspd/tspd_helpers.S
index 27fbb5a..f9a32aa 100644
--- a/services/spd/tspd/tspd_helpers.S
+++ b/services/spd/tspd/tspd_helpers.S
@@ -29,9 +29,9 @@
  */
 
 #include <context.h>
-#include <tspd_private.h>
 #include <asm_macros.S>
 #include <cm_macros.S>
+#include "tspd_private.h"
 
 	.global	tspd_enter_sp
 	/* ---------------------------------------------