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/drivers/arm/tzc400/tzc400.c b/drivers/arm/tzc400/tzc400.c
index b88e34a..ec6adee 100644
--- a/drivers/arm/tzc400/tzc400.c
+++ b/drivers/arm/tzc400/tzc400.c
@@ -29,10 +29,10 @@
  */
 
 #include <assert.h>
-#include "arch_helpers.h"
-#include "tzc400.h"
-#include "mmio.h"
-#include "debug.h"
+#include <arch_helpers.h>
+#include <tzc400.h>
+#include <mmio.h>
+#include <debug.h>
 
 static uint32_t tzc_read_build_config(uint64_t base)
 {