Move std.c to arch to avoid conflicts with libc for tests.

Change-Id: I0fc966962413ee12f84058d702e7396e38460f27
diff --git a/src/dlog.c b/src/dlog.c
index 1ce5566..a0c1d15 100644
--- a/src/dlog.c
+++ b/src/dlog.c
@@ -20,9 +20,9 @@
 #include <stddef.h>
 
 #include "hf/arch/console.h"
+#include "hf/arch/std.h"
 
 #include "hf/spinlock.h"
-#include "hf/std.h"
 
 /* Keep macro alignment */
 /* clang-format off */