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/common/bl_common.c b/common/bl_common.c
index b03165b..acdcc1f 100644
--- a/common/bl_common.c
+++ b/common/bl_common.c
@@ -37,8 +37,8 @@
 #include <platform.h>
 #include <semihosting.h>
 #include <bl_common.h>
-#include "io_storage.h"
-#include "debug.h"
+#include <io_storage.h>
+#include <debug.h>
 
 unsigned long page_align(unsigned long value, unsigned dir)
 {