Move error_code.h into otautil.

This way it stops requiring relative path ".." in LOCAL_C_INCLUDES
(uncrypt and edify). Soong doesn't accept non-local ".." in
"local_include_dirs".

Test: mmma bootable/recovery
Change-Id: Ia4649789cef2aaeb2785483660e9ea5a8b389c62

uncrypt/uncrypt.cpp

@@ -116,7 +116,7 @@
 #include <cutils/sockets.h>
 #include <fs_mgr.h>
 
-#include "error_code.h"
+#include "otautil/error_code.h"
 
 static constexpr int WINDOW_SIZE = 5;
 static constexpr int FIBMAP_RETRY_LIMIT = 3;