Move headers under the hf directory.

This helps distinguish local headers from the more official headers.

Change-Id: I535c1b44081b9d60ba63666cd1ad514aaaf2c68d
diff --git a/inc/hf/arch.h b/inc/hf/arch.h
new file mode 100644
index 0000000..fcdead1
--- /dev/null
+++ b/inc/hf/arch.h
@@ -0,0 +1,8 @@
+#ifndef _ARCH_H
+#define _ARCH_H
+
+#include "hf/cpu.h"
+
+void arch_putchar(char c);
+
+#endif /* _ARCH_H */