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/bl31/aarch64/runtime_exceptions.S b/bl31/aarch64/runtime_exceptions.S
index d00c1d7..b89a768 100644
--- a/bl31/aarch64/runtime_exceptions.S
+++ b/bl31/aarch64/runtime_exceptions.S
@@ -32,8 +32,8 @@
 #include <runtime_svc.h>
 #include <platform.h>
 #include <context.h>
-#include "asm_macros.S"
-#include "cm_macros.S"
+#include <asm_macros.S>
+#include <cm_macros.S>
 
 	.globl	runtime_exceptions
 	.globl	el3_exit