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

Change-Id: I0fc966962413ee12f84058d702e7396e38460f27
diff --git a/test/hftest/inc/hftest_impl.h b/test/hftest/inc/hftest_impl.h
index 39e50a9..2519595 100644
--- a/test/hftest/inc/hftest_impl.h
+++ b/test/hftest/inc/hftest_impl.h
@@ -18,7 +18,7 @@
 
 #include <stdnoreturn.h>
 
-#include "hf/std.h"
+#include "hf/arch/std.h"
 
 /*
  * Log with the HFTEST_LOG_PREFIX and a new line. The zero is added so there is